diff --git a/.gitignore b/.gitignore
index 052d256c2..0dca15623 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,6 +59,7 @@ lib
 # Test releated files
 test/unit/coverage
 test/e2e/reports
+report.html
 
 # Website/Docs releated files
 /website/node_modules
diff --git a/src/cli/formatter.ts b/src/cli/formatter.ts
index bca2d711a..7144eb1ac 100644
--- a/src/cli/formatter.ts
+++ b/src/cli/formatter.ts
@@ -3,7 +3,7 @@ import { EventEmitter } from 'events'
 import { sync as globSync } from 'glob'
 import { parse, resolve } from 'path'
 import type { HTMLHint as IHTMLHint } from '../core/core'
-import type { Hint, Ruleset } from '../core/types'
+import type { Configuration, Hint } from '../core/types'
 
 let HTMLHint: typeof IHTMLHint
 let options: { nocolor?: boolean }
@@ -45,7 +45,7 @@ export interface FormatterFileEvent {
 }
 
 export interface FormatterConfigEvent {
-  ruleset: Ruleset
+  config?: Configuration
   configPath?: string
 }
 
diff --git a/src/cli/htmlhint.ts b/src/cli/htmlhint.ts
index 1236feb64..44e384256 100644
--- a/src/cli/htmlhint.ts
+++ b/src/cli/htmlhint.ts
@@ -11,7 +11,7 @@ import { dirname, resolve, sep } from 'path'
 import * as request from 'request'
 import * as stripJsonComments from 'strip-json-comments'
 import type { HTMLHint as IHTMLHint } from '../core/core'
-import type { Hint, Ruleset } from '../core/types'
+import type { Configuration, Hint } from '../core/types'
 import { Formatter } from './formatter'
 
 const HTMLHint: typeof IHTMLHint = require('../htmlhint.js').HTMLHint
@@ -96,9 +96,11 @@ if (format) {
   formatter.setFormat(format)
 }
 
+// TODO: parse and validate `program.rules`
+
 hintTargets(arrTargets, {
   rulesdir: program.rulesdir,
-  ruleset: program.rules,
+  config: program.rules ? { rules: program.rules } : undefined,
   formatter: formatter,
   ignore: program.ignore,
 })
@@ -121,7 +123,7 @@ function hintTargets(
   arrTargets: string[],
   options: {
     formatter: Formatter
-    ruleset?: Ruleset
+    config?: Configuration
     rulesdir?: string
     ignore?: string
   }
@@ -213,7 +215,7 @@ function hintAllFiles(
   options: {
     ignore?: string
     formatter: Formatter
-    ruleset?: Ruleset
+    config?: Configuration
   },
   onFinised: (result: {
     targetFileCount: number
@@ -241,10 +243,10 @@ function hintAllFiles(
     time: number
   }> = []
 
-  // init ruleset
-  let ruleset = options.ruleset
-  if (ruleset === undefined) {
-    ruleset = getConfig(program.config, globInfo.base, formatter)
+  // init config
+  let config = options.config
+  if (config === undefined) {
+    config = getConfig(program.config, globInfo.base, formatter)
   }
 
   // hint queue
@@ -252,11 +254,11 @@ function hintAllFiles(
     const startTime = new Date().getTime()
 
     if (filepath === 'stdin') {
-      hintStdin(ruleset, hintNext)
+      hintStdin(config, hintNext)
     } else if (/^https?:\/\//.test(filepath)) {
-      hintUrl(filepath, ruleset, hintNext)
+      hintUrl(filepath, config, hintNext)
     } else {
-      const messages = hintFile(filepath, ruleset)
+      const messages = hintFile(filepath, config)
       hintNext(messages)
     }
 
@@ -370,7 +372,7 @@ function getConfig(
   configPath: string | undefined,
   base: string,
   formatter: Formatter
-) {
+): Configuration | undefined {
   if (configPath === undefined && existsSync(base)) {
     // find default config file in parent directory
     if (statSync(base).isDirectory() === false) {
@@ -378,6 +380,7 @@ function getConfig(
     }
 
     while (base) {
+      // TODO: load via cosmiconfig (https://github.com/htmlhint/HTMLHint/issues/126)
       const tmpConfigFile = resolve(base, '.htmlhintrc')
 
       if (existsSync(tmpConfigFile)) {
@@ -395,20 +398,22 @@ function getConfig(
 
   // TODO: can configPath be undefined here?
   if (configPath !== undefined && existsSync(configPath)) {
-    const config = readFileSync(configPath, 'utf-8')
-    let ruleset: Ruleset = {}
+    const configContent = readFileSync(configPath, 'utf-8')
+    let config: Configuration | undefined
 
     try {
-      ruleset = JSON.parse(stripJsonComments(config))
+      config = JSON.parse(stripJsonComments(configContent))
       formatter.emit('config', {
-        ruleset: ruleset,
-        configPath: configPath,
+        configPath,
+        config,
       })
     } catch (e) {
       // ignore
     }
 
-    return ruleset
+    // TODO: validate config
+
+    return config
   }
 }
 
@@ -456,7 +461,7 @@ function walkPath(
 }
 
 // hint file
-function hintFile(filepath: string, ruleset?: Ruleset) {
+function hintFile(filepath: string, config?: Configuration) {
   let content = ''
 
   try {
@@ -465,12 +470,12 @@ function hintFile(filepath: string, ruleset?: Ruleset) {
     // ignore
   }
 
-  return HTMLHint.verify(content, { rules: ruleset })
+  return HTMLHint.verify(content, config)
 }
 
 // hint stdin
 function hintStdin(
-  ruleset: Ruleset | undefined,
+  config: Configuration | undefined,
   callback: (messages: Hint[]) => void
 ) {
   process.stdin.setEncoding('utf8')
@@ -483,7 +488,7 @@ function hintStdin(
 
   process.stdin.on('end', () => {
     const content = buffers.join('')
-    const messages = HTMLHint.verify(content, { rules: ruleset })
+    const messages = HTMLHint.verify(content, config)
     callback(messages)
   })
 }
@@ -491,12 +496,12 @@ function hintStdin(
 // hint url
 function hintUrl(
   url: string,
-  ruleset: Ruleset | undefined,
+  config: Configuration | undefined,
   callback: (messages: Hint[]) => void
 ) {
   request.get(url, (error, response, body) => {
     if (!error && response.statusCode == 200) {
-      const messages = HTMLHint.verify(body, { rules: ruleset })
+      const messages = HTMLHint.verify(body, config)
       callback(messages)
     } else {
       callback([])
diff --git a/src/core/configuration.ts b/src/core/configuration.ts
new file mode 100644
index 000000000..e56853cbe
--- /dev/null
+++ b/src/core/configuration.ts
@@ -0,0 +1,39 @@
+import { Configuration } from './types'
+
+export function isConfiguration(value: unknown): value is Configuration {
+  // Config must be an object
+  if (typeof value !== 'object') {
+    return false
+  }
+
+  // Config must not be null
+  if (value === null) {
+    return false
+  }
+
+  // This helps to get better support for TypeScript
+  const config = value as Record<string, unknown>
+
+  // If extends is defined, it must be an array
+  if (config.extends !== undefined) {
+    if (!Array.isArray(config.extends)) {
+      return false
+    }
+
+    // Any value within extens must be a string
+    for (const extension of config.extends) {
+      if (typeof extension !== 'string') {
+        return false
+      }
+    }
+  }
+
+  // If extends is defined, it must be an object
+  if (config.rules !== undefined) {
+    if (typeof config.rules !== 'object' && config.rules !== null) {
+      return false
+    }
+  }
+
+  return true
+}
diff --git a/src/core/core.ts b/src/core/core.ts
index bf6c55482..9b09aa231 100644
--- a/src/core/core.ts
+++ b/src/core/core.ts
@@ -1,3 +1,4 @@
+import { isConfiguration } from './configuration'
 import HTMLParser from './htmlparser'
 import Reporter, { ReportMessageCallback } from './reporter'
 import * as HTMLRules from './rules'
@@ -15,20 +16,43 @@ export interface FormatOptions {
   indent?: number
 }
 
-class HTMLHintCore {
-  public rules: { [id: string]: Rule } = {}
-  public readonly defaultRuleset: Ruleset = {
-    'tagname-lowercase': 'error',
+const HTMLHINT_RECOMMENDED = 'htmlhint:recommended'
+const HTMLHINT_LEGACY = 'htmlhint:legacy'
+
+const DEFAULT_RULESETS: Record<string, Ruleset> = {
+  [HTMLHINT_RECOMMENDED]: {
+    'alt-require': 'warn',
+    'attr-lowercase': 'warn',
+    'attr-no-duplication': 'error',
+    'attr-no-unnecessary-whitespace': 'warn',
+    'attr-unsafe-chars': 'warn',
+    'attr-value-double-quotes': 'warn',
+    'id-class-ad-disabled': 'warn',
+    'id-unique': 'error',
+    'space-tab-mixed-disabled': 'warn',
+    'spec-char-escape': 'warn',
+    'src-not-empty': 'error',
+    'tag-pair': 'warn',
+    'tagname-lowercase': 'warn',
+    'tagname-specialchars': 'error',
+    'title-require': 'warn',
+  },
+  [HTMLHINT_LEGACY]: {
     'attr-lowercase': 'error',
+    'attr-no-duplication': 'error',
     'attr-value-double-quotes': 'error',
     'doctype-first': 'error',
-    'tag-pair': 'error',
-    'spec-char-escape': 'error',
     'id-unique': 'error',
+    'spec-char-escape': 'error',
     'src-not-empty': 'error',
-    'attr-no-duplication': 'error',
+    'tag-pair': 'error',
+    'tagname-lowercase': 'error',
     'title-require': 'error',
-  }
+  },
+}
+
+class HTMLHintCore {
+  public rules: { [id: string]: Rule } = {}
 
   public addRule(rule: Rule) {
     this.rules[rule.id] = rule
@@ -36,11 +60,34 @@ class HTMLHintCore {
 
   public verify(
     html: string,
-    config: Configuration = { rules: this.defaultRuleset }
+    config: Configuration = { extends: [HTMLHINT_RECOMMENDED] }
   ) {
-    let ruleset = config.rules ?? this.defaultRuleset
+    if (!isConfiguration(config)) {
+      throw new Error('The HTMLHint configuration is invalid')
+    }
+
+    let ruleset: Ruleset = {}
+
+    // If an empty configuration is passed, use the recommended ruleset
+    if (config.extends === undefined && config.rules === undefined) {
+      config.extends = [HTMLHINT_RECOMMENDED]
+    }
+
+    // Iterate through extensions and merge rulesets into ruleset
+    for (const extend of config.extends ?? []) {
+      if (typeof extend === 'string') {
+        const extendRuleset = DEFAULT_RULESETS[extend] ?? {}
+        ruleset = { ...ruleset, ...extendRuleset }
+      }
+    }
+
+    // Apply self-configured rules
+    ruleset = { ...ruleset, ...(config.rules ?? {}) }
+
+    // If no rules have been configured, return immediately
     if (Object.keys(ruleset).length === 0) {
-      ruleset = this.defaultRuleset
+      // console.log('Please configure some HTMLHint rules')
+      return []
     }
 
     // parse inline ruleset
diff --git a/src/core/types.ts b/src/core/types.ts
index 959ca4824..c8310ec8d 100644
--- a/src/core/types.ts
+++ b/src/core/types.ts
@@ -2,6 +2,7 @@ import { HTMLParser } from './core'
 import { ReportMessageCallback } from './reporter'
 
 export interface Configuration {
+  extends?: string[]
   rules?: Ruleset
 }
 
diff --git a/test/cli/formatters/checkstyle.spec.js b/test/cli/formatters/checkstyle.spec.js
index 7ab2af9b7..35dd11aba 100644
--- a/test/cli/formatters/checkstyle.spec.js
+++ b/test/cli/formatters/checkstyle.spec.js
@@ -6,7 +6,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: checkstyle', () => {
-    it('should have stdout output with formatter checkstyle', (done) => {
+    it('Should have stdout output with formatter checkstyle', (done) => {
       const expected = fs
         .readFileSync(path.resolve(__dirname, 'checkstyle.xml'), 'utf8')
         .replace('{{path}}', path.resolve(__dirname, 'example.html'))
diff --git a/test/cli/formatters/checkstyle.xml b/test/cli/formatters/checkstyle.xml
index aa96f0fc7..5d8fdcbfd 100644
--- a/test/cli/formatters/checkstyle.xml
+++ b/test/cli/formatters/checkstyle.xml
@@ -1,25 +1,25 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <checkstyle version="4.3">
     <file name="{{path}}">
-        <error line="8" column="7" severity="error" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
-        <error line="8" column="14" severity="error" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
         <error line="8" column="14" severity="error" message="Duplicate of attribute name [ bad ] was found." source="htmlhint.attr-no-duplication"/>
-        <error line="9" column="7" severity="error" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
-        <error line="9" column="14" severity="error" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="8" column="7" severity="warning" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="8" column="14" severity="warning" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
         <error line="9" column="14" severity="error" message="Duplicate of attribute name [ bad ] was found." source="htmlhint.attr-no-duplication"/>
-        <error line="10" column="22" severity="error" message="Tag must be paired, no start tag: [ &lt;/input&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="11" column="3" severity="error" message="Special characters must be escaped : [ &lt; ]." source="htmlhint.spec-char-escape"/>
-        <error line="11" column="18" severity="error" message="Special characters must be escaped : [ &gt; ]." source="htmlhint.spec-char-escape"/>
-        <error line="13" column="11" severity="error" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="14" column="9" severity="error" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="15" column="7" severity="error" message="Tag must be paired, no start tag: [ &lt;/hello&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="16" column="5" severity="error" message="Tag must be paired, no start tag: [ &lt;/test&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="17" column="3" severity="error" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="21" column="15" severity="error" message="The value of attribute [ class ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
-        <error line="21" column="24" severity="error" message="The value of attribute [ what ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
-        <error line="21" column="32" severity="error" message="The value of attribute [ something ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
-        <error line="25" column="3" severity="error" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="26" column="1" severity="error" message="Tag must be paired, no start tag: [ &lt;/bad&gt; ]" source="htmlhint.tag-pair"/>
-        <error line="27" column="1" severity="error" message="Tag must be paired, no start tag: [ &lt;/bad&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="9" column="7" severity="warning" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="9" column="14" severity="warning" message="The value of attribute [ bad ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="10" column="22" severity="warning" message="Tag must be paired, no start tag: [ &lt;/input&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="11" column="3" severity="warning" message="Special characters must be escaped : [ &lt; ]." source="htmlhint.spec-char-escape"/>
+        <error line="11" column="18" severity="warning" message="Special characters must be escaped : [ &gt; ]." source="htmlhint.spec-char-escape"/>
+        <error line="13" column="11" severity="warning" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="14" column="9" severity="warning" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="15" column="7" severity="warning" message="Tag must be paired, no start tag: [ &lt;/hello&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="16" column="5" severity="warning" message="Tag must be paired, no start tag: [ &lt;/test&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="17" column="3" severity="warning" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="21" column="15" severity="warning" message="The value of attribute [ class ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="21" column="24" severity="warning" message="The value of attribute [ what ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="21" column="32" severity="warning" message="The value of attribute [ something ] must be in double quotes." source="htmlhint.attr-value-double-quotes"/>
+        <error line="25" column="3" severity="warning" message="Tag must be paired, no start tag: [ &lt;/div&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="26" column="1" severity="warning" message="Tag must be paired, no start tag: [ &lt;/bad&gt; ]" source="htmlhint.tag-pair"/>
+        <error line="27" column="1" severity="warning" message="Tag must be paired, no start tag: [ &lt;/bad&gt; ]" source="htmlhint.tag-pair"/>
     </file>
 </checkstyle>
diff --git a/test/cli/formatters/compact.spec.js b/test/cli/formatters/compact.spec.js
index cd0f8d324..dcb1ebcc6 100644
--- a/test/cli/formatters/compact.spec.js
+++ b/test/cli/formatters/compact.spec.js
@@ -6,7 +6,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: compact', () => {
-    it('should have stdout output with formatter compact', (done) => {
+    it('Should have stdout output with formatter compact', (done) => {
       const expected = fs
         .readFileSync(path.resolve(__dirname, 'compact.txt'), 'utf8')
         .replace(
diff --git a/test/cli/formatters/compact.txt b/test/cli/formatters/compact.txt
index 07dee1834..6d850ffc6 100644
--- a/test/cli/formatters/compact.txt
+++ b/test/cli/formatters/compact.txt
@@ -1,94 +1,94 @@
-{{path}}: line 8, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 8, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 8, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 9, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 9, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 8, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 8, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 9, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 10, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 10, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 9, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 9, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 10, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 11, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 11, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 10, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 10, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 11, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 12, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 12, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 11, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 11, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 12, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 13, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 13, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 12, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 12, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 13, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 14, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 14, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 13, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 13, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 14, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 15, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 15, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 14, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 14, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 15, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 16, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 16, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 15, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 15, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 16, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 17, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 17, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 16, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 16, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 17, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 18, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 18, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 17, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 17, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 18, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 19, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 19, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 18, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 18, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 19, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 20, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 20, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 19, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 19, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 20, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 21, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 21, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 20, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 20, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 21, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 22, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 22, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 21, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 21, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 22, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 23, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 23, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 22, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 22, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 23, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 24, col 7, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 24, col 14, error - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 23, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 23, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
 {{path}}: line 24, col 14, error - Duplicate of attribute name [ bad ] was found. (attr-no-duplication)
-{{path}}: line 25, col 22, error - Tag must be paired, no start tag: [ </input> ] (tag-pair)
-{{path}}: line 26, col 3, error - Special characters must be escaped : [ < ]. (spec-char-escape)
-{{path}}: line 26, col 18, error - Special characters must be escaped : [ > ]. (spec-char-escape)
-{{path}}: line 28, col 11, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 29, col 9, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 30, col 7, error - Tag must be paired, no start tag: [ </hello> ] (tag-pair)
-{{path}}: line 31, col 5, error - Tag must be paired, no start tag: [ </test> ] (tag-pair)
-{{path}}: line 32, col 3, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 38, col 19, error - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 38, col 28, error - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 38, col 36, error - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 44, col 3, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 50, col 19, error - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 50, col 28, error - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 50, col 36, error - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 56, col 3, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 62, col 19, error - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 62, col 28, error - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 62, col 36, error - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 68, col 3, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 74, col 19, error - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 74, col 28, error - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 74, col 36, error - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
-{{path}}: line 80, col 3, error - Tag must be paired, no start tag: [ </div> ] (tag-pair)
-{{path}}: line 81, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 82, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 83, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 84, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 85, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 86, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 87, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 88, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 89, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 90, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 91, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 92, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 93, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 94, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 95, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 96, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
-{{path}}: line 97, col 1, error - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 24, col 7, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 24, col 14, warning - The value of attribute [ bad ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 25, col 22, warning - Tag must be paired, no start tag: [ </input> ] (tag-pair)
+{{path}}: line 26, col 3, warning - Special characters must be escaped : [ < ]. (spec-char-escape)
+{{path}}: line 26, col 18, warning - Special characters must be escaped : [ > ]. (spec-char-escape)
+{{path}}: line 28, col 11, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 29, col 9, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 30, col 7, warning - Tag must be paired, no start tag: [ </hello> ] (tag-pair)
+{{path}}: line 31, col 5, warning - Tag must be paired, no start tag: [ </test> ] (tag-pair)
+{{path}}: line 32, col 3, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 38, col 19, warning - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 38, col 28, warning - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 38, col 36, warning - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 44, col 3, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 50, col 19, warning - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 50, col 28, warning - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 50, col 36, warning - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 56, col 3, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 62, col 19, warning - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 62, col 28, warning - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 62, col 36, warning - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 68, col 3, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 74, col 19, warning - The value of attribute [ class ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 74, col 28, warning - The value of attribute [ what ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 74, col 36, warning - The value of attribute [ something ] must be in double quotes. (attr-value-double-quotes)
+{{path}}: line 80, col 3, warning - Tag must be paired, no start tag: [ </div> ] (tag-pair)
+{{path}}: line 81, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 82, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 83, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 84, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 85, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 86, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 87, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 88, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 89, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 90, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 91, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 92, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 93, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 94, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 95, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 96, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
+{{path}}: line 97, col 1, warning - Tag must be paired, no start tag: [ </bad> ] (tag-pair)
 
 \u001b[31m92 problems\u001b[39m
diff --git a/test/cli/formatters/default.spec.js b/test/cli/formatters/default.spec.js
index 0c84c1da4..caa41e39c 100644
--- a/test/cli/formatters/default.spec.js
+++ b/test/cli/formatters/default.spec.js
@@ -5,7 +5,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: default', () => {
-    it('should have stdout output with formatter default', (done) => {
+    it('Should have stdout output with formatter default', (done) => {
       ChildProcess.exec(
         [
           'node',
diff --git a/test/cli/formatters/html.html b/test/cli/formatters/html.html
index b335e82d2..ec71e2f65 100644
--- a/test/cli/formatters/html.html
+++ b/test/cli/formatters/html.html
@@ -1 +1 @@
-<html><head><title>HTML Hint Violation Report</title></head><body><center><h2>Violation Report</h2></center><table border="1"><tr><th>Number#</th><th>File Name</th><th>Line Number</th><th>Message</th></tr><tr><td>1</td><td>{{path}}</td><td>8</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>2</td><td>{{path}}</td><td>8</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>3</td><td>{{path}}</td><td>8</td><td>Duplicate of attribute name [ bad ] was found.</td></tr><tr><td>4</td><td>{{path}}</td><td>9</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>5</td><td>{{path}}</td><td>9</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>6</td><td>{{path}}</td><td>9</td><td>Duplicate of attribute name [ bad ] was found.</td></tr><tr><td>7</td><td>{{path}}</td><td>10</td><td>Tag must be paired, no start tag: [ </input> ]</td></tr><tr><td>8</td><td>{{path}}</td><td>11</td><td>Special characters must be escaped : [ < ].</td></tr><tr><td>9</td><td>{{path}}</td><td>11</td><td>Special characters must be escaped : [ > ].</td></tr><tr><td>10</td><td>{{path}}</td><td>13</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>11</td><td>{{path}}</td><td>14</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>12</td><td>{{path}}</td><td>15</td><td>Tag must be paired, no start tag: [ </hello> ]</td></tr><tr><td>13</td><td>{{path}}</td><td>16</td><td>Tag must be paired, no start tag: [ </test> ]</td></tr><tr><td>14</td><td>{{path}}</td><td>17</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>15</td><td>{{path}}</td><td>21</td><td>The value of attribute [ class ] must be in double quotes.</td></tr><tr><td>16</td><td>{{path}}</td><td>21</td><td>The value of attribute [ what ] must be in double quotes.</td></tr><tr><td>17</td><td>{{path}}</td><td>21</td><td>The value of attribute [ something ] must be in double quotes.</td></tr><tr><td>18</td><td>{{path}}</td><td>25</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>19</td><td>{{path}}</td><td>26</td><td>Tag must be paired, no start tag: [ </bad> ]</td></tr><tr><td>20</td><td>{{path}}</td><td>27</td><td>Tag must be paired, no start tag: [ </bad> ]</td></tr></table></body></html>
+<html><head><title>HTML Hint Violation Report</title></head><body><center><h2>Violation Report</h2></center><table border="1"><tr><th>Number#</th><th>File Name</th><th>Line Number</th><th>Message</th></tr><tr><td>1</td><td>{{path}}</td><td>8</td><td>Duplicate of attribute name [ bad ] was found.</td></tr><tr><td>2</td><td>{{path}}</td><td>8</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>3</td><td>{{path}}</td><td>8</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>4</td><td>{{path}}</td><td>9</td><td>Duplicate of attribute name [ bad ] was found.</td></tr><tr><td>5</td><td>{{path}}</td><td>9</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>6</td><td>{{path}}</td><td>9</td><td>The value of attribute [ bad ] must be in double quotes.</td></tr><tr><td>7</td><td>{{path}}</td><td>10</td><td>Tag must be paired, no start tag: [ </input> ]</td></tr><tr><td>8</td><td>{{path}}</td><td>11</td><td>Special characters must be escaped : [ < ].</td></tr><tr><td>9</td><td>{{path}}</td><td>11</td><td>Special characters must be escaped : [ > ].</td></tr><tr><td>10</td><td>{{path}}</td><td>13</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>11</td><td>{{path}}</td><td>14</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>12</td><td>{{path}}</td><td>15</td><td>Tag must be paired, no start tag: [ </hello> ]</td></tr><tr><td>13</td><td>{{path}}</td><td>16</td><td>Tag must be paired, no start tag: [ </test> ]</td></tr><tr><td>14</td><td>{{path}}</td><td>17</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>15</td><td>{{path}}</td><td>21</td><td>The value of attribute [ class ] must be in double quotes.</td></tr><tr><td>16</td><td>{{path}}</td><td>21</td><td>The value of attribute [ what ] must be in double quotes.</td></tr><tr><td>17</td><td>{{path}}</td><td>21</td><td>The value of attribute [ something ] must be in double quotes.</td></tr><tr><td>18</td><td>{{path}}</td><td>25</td><td>Tag must be paired, no start tag: [ </div> ]</td></tr><tr><td>19</td><td>{{path}}</td><td>26</td><td>Tag must be paired, no start tag: [ </bad> ]</td></tr><tr><td>20</td><td>{{path}}</td><td>27</td><td>Tag must be paired, no start tag: [ </bad> ]</td></tr></table></body></html>
diff --git a/test/cli/formatters/html.spec.js b/test/cli/formatters/html.spec.js
index 67e38d171..d780de863 100644
--- a/test/cli/formatters/html.spec.js
+++ b/test/cli/formatters/html.spec.js
@@ -6,7 +6,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: html', () => {
-    it('should have stdout output with formatter html', (done) => {
+    it('Should have stdout output with formatter html', (done) => {
       const expected = fs
         .readFileSync(path.resolve(__dirname, 'html.html'), 'utf8')
         .replace(/\{\{path\}\}/g, path.resolve(__dirname, 'example.html'))
diff --git a/test/cli/formatters/json.json b/test/cli/formatters/json.json
index 8744fe391..f8446bd10 100644
--- a/test/cli/formatters/json.json
+++ b/test/cli/formatters/json.json
@@ -4,6 +4,19 @@
     "messages": [
       {
         "type": "error",
+        "message": "Duplicate of attribute name [ bad ] was found.",
+        "raw": " bad=''",
+        "evidence": "  <div bad='' bad=''></div>",
+        "line": 8,
+        "col": 14,
+        "rule": {
+          "id": "attr-no-duplication",
+          "description": "Elements cannot have duplicate attributes.",
+          "link": "https://github.com/thedaviddias/HTMLHint/wiki/attr-no-duplication"
+        }
+      },
+      {
+        "type": "warning",
         "message": "The value of attribute [ bad ] must be in double quotes.",
         "raw": " bad=''",
         "evidence": "  <div bad='' bad=''></div>",
@@ -16,7 +29,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "The value of attribute [ bad ] must be in double quotes.",
         "raw": " bad=''",
         "evidence": "  <div bad='' bad=''></div>",
@@ -33,7 +46,7 @@
         "message": "Duplicate of attribute name [ bad ] was found.",
         "raw": " bad=''",
         "evidence": "  <div bad='' bad=''></div>",
-        "line": 8,
+        "line": 9,
         "col": 14,
         "rule": {
           "id": "attr-no-duplication",
@@ -42,7 +55,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "The value of attribute [ bad ] must be in double quotes.",
         "raw": " bad=''",
         "evidence": "  <div bad='' bad=''></div>",
@@ -55,7 +68,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "The value of attribute [ bad ] must be in double quotes.",
         "raw": " bad=''",
         "evidence": "  <div bad='' bad=''></div>",
@@ -68,20 +81,7 @@
         }
       },
       {
-        "type": "error",
-        "message": "Duplicate of attribute name [ bad ] was found.",
-        "raw": " bad=''",
-        "evidence": "  <div bad='' bad=''></div>",
-        "line": 9,
-        "col": 14,
-        "rule": {
-          "id": "attr-no-duplication",
-          "description": "Elements cannot have duplicate attributes.",
-          "link": "https://github.com/thedaviddias/HTMLHint/wiki/attr-no-duplication"
-        }
-      },
-      {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </input> ]",
         "raw": "</input>",
         "evidence": "  <input type=\"text\"></input>",
@@ -94,7 +94,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Special characters must be escaped : [ < ].",
         "raw": "\n  <div class\"foo\">\n\n          ",
         "evidence": "  <div class\"foo\">",
@@ -107,7 +107,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Special characters must be escaped : [ > ].",
         "raw": "\n  <div class\"foo\">\n\n          ",
         "evidence": "  <div class\"foo\">",
@@ -120,7 +120,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </div> ]",
         "raw": "</div>",
         "evidence": "          </div>",
@@ -133,7 +133,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </div> ]",
         "raw": "</div>",
         "evidence": "        </div>",
@@ -146,7 +146,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </hello> ]",
         "raw": "</hello>",
         "evidence": "      </hello>",
@@ -159,7 +159,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </test> ]",
         "raw": "</test>",
         "evidence": "    </test>",
@@ -172,7 +172,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </div> ]",
         "raw": "</div>",
         "evidence": "  </div>",
@@ -185,7 +185,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "The value of attribute [ class ] must be in double quotes.",
         "raw": " class=''",
         "evidence": "          <div class='' what='' something=''></div>",
@@ -198,7 +198,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "The value of attribute [ what ] must be in double quotes.",
         "raw": " what=''",
         "evidence": "          <div class='' what='' something=''></div>",
@@ -211,7 +211,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "The value of attribute [ something ] must be in double quotes.",
         "raw": " something=''",
         "evidence": "          <div class='' what='' something=''></div>",
@@ -224,7 +224,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </div> ]",
         "raw": "</div>",
         "evidence": "  </div>",
@@ -237,7 +237,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </bad> ]",
         "raw": "</bad>",
         "evidence": "</bad>",
@@ -250,7 +250,7 @@
         }
       },
       {
-        "type": "error",
+        "type": "warning",
         "message": "Tag must be paired, no start tag: [ </bad> ]",
         "raw": "</bad>",
         "evidence": "</bad>",
@@ -263,6 +263,6 @@
         }
       }
     ],
-    "time": 2
+    "time": 17
   }
 ]
diff --git a/test/cli/formatters/json.spec.js b/test/cli/formatters/json.spec.js
index 7f73e35c2..85d21a3ec 100644
--- a/test/cli/formatters/json.spec.js
+++ b/test/cli/formatters/json.spec.js
@@ -6,7 +6,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: json', () => {
-    it('should have stdout output with formatter json', (done) => {
+    it('Should have stdout output with formatter json', (done) => {
       const expectedFileContent = fs
         .readFileSync(path.resolve(__dirname, 'json.json'), 'utf8')
         .replace(
diff --git a/test/cli/formatters/junit.spec.js b/test/cli/formatters/junit.spec.js
index 1954fe49d..2d60a6710 100644
--- a/test/cli/formatters/junit.spec.js
+++ b/test/cli/formatters/junit.spec.js
@@ -6,7 +6,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: junit', () => {
-    it('should have stdout output with formatter junit', (done) => {
+    it('Should have stdout output with formatter junit', (done) => {
       ChildProcess.exec(
         [
           'node',
diff --git a/test/cli/formatters/markdown.spec.js b/test/cli/formatters/markdown.spec.js
index ed9d7fe02..61d759d34 100644
--- a/test/cli/formatters/markdown.spec.js
+++ b/test/cli/formatters/markdown.spec.js
@@ -5,7 +5,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: markdown', () => {
-    it('should have stdout output with formatter markdown', (done) => {
+    it('Should have stdout output with formatter markdown', (done) => {
       ChildProcess.exec(
         [
           'node',
@@ -19,7 +19,7 @@ describe('CLI', () => {
           expect(error.code).to.be.equal(1)
 
           expect(stdout).to.contain('# TOC')
-          expect(stdout).to.contain('Found 20 errors, 0 warnings')
+          expect(stdout).to.contain('Found 2 errors, 18 warnings')
           expect(stdout).to.contain('example.html')
           expect(stdout).to.contain(
             '^ Tag must be paired, no start tag: [ </bad> ] (tag-pair)'
diff --git a/test/cli/formatters/unix.spec.js b/test/cli/formatters/unix.spec.js
index bee9348b6..aded1403a 100644
--- a/test/cli/formatters/unix.spec.js
+++ b/test/cli/formatters/unix.spec.js
@@ -6,7 +6,7 @@ const path = require('path')
 
 describe('CLI', () => {
   describe('Formatter: unix', () => {
-    it('should have stdout output with formatter unix', (done) => {
+    it('Should have stdout output with formatter unix', (done) => {
       const expected = fs
         .readFileSync(path.resolve(__dirname, 'unix.txt'), 'utf8')
         .replace(
diff --git a/test/cli/formatters/unix.txt b/test/cli/formatters/unix.txt
index decd9aef9..5e2ad2d4a 100644
--- a/test/cli/formatters/unix.txt
+++ b/test/cli/formatters/unix.txt
@@ -1,94 +1,94 @@
-{{path}}:8:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:8:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
 {{path}}:8:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:9:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:9:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:8:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:8:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:9:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:10:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:10:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:9:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:9:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:10:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:11:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:11:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:10:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:10:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:11:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:12:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:12:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:11:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:11:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:12:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:13:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:13:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:12:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:12:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:13:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:14:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:14:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:13:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:13:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:14:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:15:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:15:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:14:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:14:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:15:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:16:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:16:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:15:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:15:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:16:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:17:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:17:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:16:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:16:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:17:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:18:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:18:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:17:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:17:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:18:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:19:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:19:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:18:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:18:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:19:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:20:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:20:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:19:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:19:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:20:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:21:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:21:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:20:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:20:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:21:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:22:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:22:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:21:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:21:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:22:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:23:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:23:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:22:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:22:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:23:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:24:7: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:24:14: The value of attribute [ bad ] must be in double quotes. [error/attr-value-double-quotes]
+{{path}}:23:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:23:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
 {{path}}:24:14: Duplicate of attribute name [ bad ] was found. [error/attr-no-duplication]
-{{path}}:25:22: Tag must be paired, no start tag: [ </input> ] [error/tag-pair]
-{{path}}:26:3: Special characters must be escaped : [ < ]. [error/spec-char-escape]
-{{path}}:26:18: Special characters must be escaped : [ > ]. [error/spec-char-escape]
-{{path}}:28:11: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:29:9: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:30:7: Tag must be paired, no start tag: [ </hello> ] [error/tag-pair]
-{{path}}:31:5: Tag must be paired, no start tag: [ </test> ] [error/tag-pair]
-{{path}}:32:3: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:38:19: The value of attribute [ class ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:38:28: The value of attribute [ what ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:38:36: The value of attribute [ something ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:44:3: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:50:19: The value of attribute [ class ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:50:28: The value of attribute [ what ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:50:36: The value of attribute [ something ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:56:3: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:62:19: The value of attribute [ class ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:62:28: The value of attribute [ what ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:62:36: The value of attribute [ something ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:68:3: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:74:19: The value of attribute [ class ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:74:28: The value of attribute [ what ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:74:36: The value of attribute [ something ] must be in double quotes. [error/attr-value-double-quotes]
-{{path}}:80:3: Tag must be paired, no start tag: [ </div> ] [error/tag-pair]
-{{path}}:81:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:82:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:83:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:84:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:85:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:86:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:87:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:88:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:89:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:90:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:91:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:92:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:93:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:94:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:95:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:96:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
-{{path}}:97:1: Tag must be paired, no start tag: [ </bad> ] [error/tag-pair]
+{{path}}:24:7: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:24:14: The value of attribute [ bad ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:25:22: Tag must be paired, no start tag: [ </input> ] [warning/tag-pair]
+{{path}}:26:3: Special characters must be escaped : [ < ]. [warning/spec-char-escape]
+{{path}}:26:18: Special characters must be escaped : [ > ]. [warning/spec-char-escape]
+{{path}}:28:11: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:29:9: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:30:7: Tag must be paired, no start tag: [ </hello> ] [warning/tag-pair]
+{{path}}:31:5: Tag must be paired, no start tag: [ </test> ] [warning/tag-pair]
+{{path}}:32:3: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:38:19: The value of attribute [ class ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:38:28: The value of attribute [ what ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:38:36: The value of attribute [ something ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:44:3: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:50:19: The value of attribute [ class ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:50:28: The value of attribute [ what ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:50:36: The value of attribute [ something ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:56:3: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:62:19: The value of attribute [ class ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:62:28: The value of attribute [ what ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:62:36: The value of attribute [ something ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:68:3: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:74:19: The value of attribute [ class ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:74:28: The value of attribute [ what ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:74:36: The value of attribute [ something ] must be in double quotes. [warning/attr-value-double-quotes]
+{{path}}:80:3: Tag must be paired, no start tag: [ </div> ] [warning/tag-pair]
+{{path}}:81:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:82:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:83:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:84:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:85:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:86:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:87:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:88:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:89:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:90:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:91:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:92:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:93:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:94:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:95:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:96:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
+{{path}}:97:1: Tag must be paired, no start tag: [ </bad> ] [warning/tag-pair]
 
 \u001b[31m92 problems\u001b[39m
diff --git a/test/core.spec.js b/test/core.spec.js
index b7eddb548..c719911fa 100644
--- a/test/core.spec.js
+++ b/test/core.spec.js
@@ -1,95 +1,129 @@
 const expect = require('expect.js')
 
+/** @type import('../src/core/core').HTMLHint */
 const HTMLHint = require('../dist/htmlhint.js').HTMLHint
 
 describe('Core', () => {
-  it('Set false to rule no effected should result in an error', () => {
-    const code = '<img src="test.gif" />'
-    const messages = HTMLHint.verify(code, { rules: { 'alt-require': 'off' } })
-    expect(messages.length).to.be(0)
-  })
-
-  it('Not load default ruleset when use undefined ruleset should result in an error', () => {
-    const code =
-      '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
-    const messages = HTMLHint.verify(code)
-    expect(messages.length).to.be(9)
-  })
+  describe('Defaults', () => {
+    it('Should use the recommended ruleset, if configuration is not defined', () => {
+      const code =
+        '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
+      const messages = HTMLHint.verify(code)
+      expect(messages.length).to.be(9)
+    })
 
-  it('Not load default ruleset when use empty ruleset should result in an error', () => {
-    const code =
-      '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
-    const messages = HTMLHint.verify(code, {})
-    expect(messages.length).to.be(9)
-  })
+    it('Should use the recommended ruleset, if empty configuration is passed', () => {
+      const code =
+        '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
+      const messages = HTMLHint.verify(code, {})
+      expect(messages.length).to.be(9)
+    })
 
-  it('Inline ruleset not worked should result in an error', () => {
-    // With value = 'error'
-    let code = '<!-- htmlhint alt-require:error -->\r\n<img src="test.gif" />'
-    let messages = HTMLHint.verify(code, {
-      rules: {
-        'alt-require': 'off',
-      },
+    it('Should use the legacy ruleset, if it is passed', () => {
+      const code =
+        '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
+      const messages = HTMLHint.verify(code, {
+        extends: ['htmlhint:legacy'],
+      })
+      expect(messages.length).to.be(9)
     })
 
-    expect(messages.length).to.be(1)
-    expect(messages[0].rule.id).to.be('alt-require')
-    expect(messages[0].line).to.be(2)
-    expect(messages[0].col).to.be(5)
-
-    // Without value
-    code = '<!-- htmlhint alt-require -->\r\n<img src="test.gif" />'
-    messages = HTMLHint.verify(code, {
-      rules: {
-        'alt-require': 'off',
-      },
+    it('Should use the recommended ruleset, if it is passed', () => {
+      const code =
+        '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
+      const messages = HTMLHint.verify(code, {
+        extends: ['htmlhint:recommended'],
+      })
+      expect(messages.length).to.be(9)
     })
 
-    expect(messages.length).to.be(1)
-    expect(messages[0].rule.id).to.be('alt-require')
-    expect(messages[0].line).to.be(2)
-    expect(messages[0].col).to.be(5)
-
-    // With value = 'off'
-    code = '<!-- htmlhint alt-require:off -->\r\n<img src="test.gif" />'
-    messages = HTMLHint.verify(code, {
-      rules: {
-        'alt-require': 'error',
-      },
+    it('Should use no ruleset, if extends is not defined and empty ruleset is passed', () => {
+      const code =
+        '<P ATTR=\'1\' id="a">><div id="a"><img src="" a="1" a="2"/></div>'
+      const messages = HTMLHint.verify(code, { rules: {} })
+      expect(messages.length).to.be(0)
     })
-    expect(messages.length).to.be(0)
-
-    // Without rule
-    code = '<!-- htmlhint -->\r\n<img src="test.gif" />'
-    messages = HTMLHint.verify(code, {
-      rules: {
-        'alt-require': 'off',
-      },
+  })
+
+  describe('Customization', () => {
+    it('Set false to rule no effected should result in an error', () => {
+      const code = '<img src="test.gif" />'
+      const messages = HTMLHint.verify(code, {
+        rules: {
+          'alt-require': 'off',
+        },
+      })
+      expect(messages.length).to.be(0)
     })
 
-    expect(messages.length).to.be(0)
-  })
+    it('Inline ruleset not worked should result in an error', () => {
+      // With value = 'error'
+      let code = '<!-- htmlhint alt-require:error -->\r\n<img src="test.gif" />'
+      let messages = HTMLHint.verify(code, {
+        rules: {
+          'alt-require': 'off',
+        },
+      })
+
+      expect(messages.length).to.be(1)
+      expect(messages[0].rule.id).to.be('alt-require')
+      expect(messages[0].line).to.be(2)
+      expect(messages[0].col).to.be(5)
+
+      // Without value
+      code = '<!-- htmlhint alt-require -->\r\n<img src="test.gif" />'
+      messages = HTMLHint.verify(code, {
+        rules: {
+          'alt-require': 'off',
+        },
+      })
+
+      expect(messages.length).to.be(1)
+      expect(messages[0].rule.id).to.be('alt-require')
+      expect(messages[0].line).to.be(2)
+      expect(messages[0].col).to.be(5)
 
-  it('Show formated result should not result in an error', () => {
-    const code =
-      'tttttttttttttttttttttttttttttttttttt<div>中文<img src="test.gif" />tttttttttttttttttttttttttttttttttttttttttttttt'
-    const messages = HTMLHint.verify(code, {
-      rules: {
-        'tag-pair': 'error',
-        'alt-require': 'error',
-      },
+      // With value = 'off'
+      code = '<!-- htmlhint alt-require:off -->\r\n<img src="test.gif" />'
+      messages = HTMLHint.verify(code, {
+        rules: {
+          'alt-require': 'error',
+        },
+      })
+      expect(messages.length).to.be(0)
+
+      // Without rule
+      code = '<!-- htmlhint -->\r\n<img src="test.gif" />'
+      messages = HTMLHint.verify(code, {
+        rules: {
+          'alt-require': 'off',
+        },
+      })
+
+      expect(messages.length).to.be(0)
     })
-    let arrLogs = HTMLHint.format(messages)
-    expect(arrLogs.length).to.be(4)
 
-    arrLogs = HTMLHint.format(messages, {
-      colors: true,
-      indent: 4,
+    it('Show formated result should not result in an error', () => {
+      const code =
+        'tttttttttttttttttttttttttttttttttttt<div>中文<img src="test.gif" />tttttttttttttttttttttttttttttttttttttttttttttt'
+      const messages = HTMLHint.verify(code, {
+        rules: {
+          'alt-require': 'error',
+          'tag-pair': 'error',
+        },
+      })
+      let arrLogs = HTMLHint.format(messages)
+      expect(arrLogs.length).to.be(4)
+
+      arrLogs = HTMLHint.format(messages, {
+        colors: true,
+        indent: 4,
+      })
+      const log = arrLogs[0]
+      expect(/\[37m/.test(log)).to.be(true)
+      expect(/ {4}L1 /.test(log)).to.be(true)
+      expect(/|\.\.\./.test(log)).to.be(true)
+      expect(/t\.\.\./.test(log)).to.be(true)
     })
-    const log = arrLogs[0]
-    expect(/\[37m/.test(log)).to.be(true)
-    expect(/ {4}L1 /.test(log)).to.be(true)
-    expect(/|\.\.\./.test(log)).to.be(true)
-    expect(/t\.\.\./.test(log)).to.be(true)
   })
 })
diff --git a/test/htmlparser.spec.js b/test/htmlparser.spec.js
index 1b5f8e743..2dcadfde1 100644
--- a/test/htmlparser.spec.js
+++ b/test/htmlparser.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../src/core/core').HTMLParser */
 const HTMLParser = require('../dist/htmlhint.js').HTMLParser
 
 expect.Assertion.prototype.event = function (type, attr) {
diff --git a/test/rules/alt-require.spec.js b/test/rules/alt-require.spec.js
index f79347e5b..067b90d46 100644
--- a/test/rules/alt-require.spec.js
+++ b/test/rules/alt-require.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'alt-require'
diff --git a/test/rules/attr-lowercase.spec.js b/test/rules/attr-lowercase.spec.js
index 3164cdfb7..0654f8325 100644
--- a/test/rules/attr-lowercase.spec.js
+++ b/test/rules/attr-lowercase.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-lowercase'
diff --git a/test/rules/attr-no-duplication.spec.js b/test/rules/attr-no-duplication.spec.js
index e1fba4edb..974c3fbdf 100644
--- a/test/rules/attr-no-duplication.spec.js
+++ b/test/rules/attr-no-duplication.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-no-duplication'
diff --git a/test/rules/attr-no-unnecessary-whitespace.spec.js b/test/rules/attr-no-unnecessary-whitespace.spec.js
index 0a8e1d79e..ddd9726d4 100644
--- a/test/rules/attr-no-unnecessary-whitespace.spec.js
+++ b/test/rules/attr-no-unnecessary-whitespace.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-no-unnecessary-whitespace'
diff --git a/test/rules/attr-sort.spec.js b/test/rules/attr-sort.spec.js
index a12f2269a..06b4dd919 100644
--- a/test/rules/attr-sort.spec.js
+++ b/test/rules/attr-sort.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruleId = 'attr-sorted'
diff --git a/test/rules/attr-unsafe-chars.spec.js b/test/rules/attr-unsafe-chars.spec.js
index 1ca55ef0b..db539c528 100644
--- a/test/rules/attr-unsafe-chars.spec.js
+++ b/test/rules/attr-unsafe-chars.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-unsafe-chars'
diff --git a/test/rules/attr-value-double-quotes.spec.js b/test/rules/attr-value-double-quotes.spec.js
index 06ea4a030..3d778e4a5 100644
--- a/test/rules/attr-value-double-quotes.spec.js
+++ b/test/rules/attr-value-double-quotes.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-value-double-quotes'
diff --git a/test/rules/attr-value-not-empty.spec.js b/test/rules/attr-value-not-empty.spec.js
index ced884191..66ef4b10b 100644
--- a/test/rules/attr-value-not-empty.spec.js
+++ b/test/rules/attr-value-not-empty.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-value-not-empty'
diff --git a/test/rules/attr-value-single-quotes.spec.js b/test/rules/attr-value-single-quotes.spec.js
index 2660c9b70..8440be096 100644
--- a/test/rules/attr-value-single-quotes.spec.js
+++ b/test/rules/attr-value-single-quotes.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-value-single-quotes'
diff --git a/test/rules/attr-whitespace.spec.js b/test/rules/attr-whitespace.spec.js
index 5f0ba5f62..d27e91ff6 100644
--- a/test/rules/attr-whitespace.spec.js
+++ b/test/rules/attr-whitespace.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'attr-whitespace'
diff --git a/test/rules/default.spec.js b/test/rules/default.spec.js
index a8b6f213b..e729b27d1 100644
--- a/test/rules/default.spec.js
+++ b/test/rules/default.spec.js
@@ -1,11 +1,12 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 describe('Rules: default', () => {
-  it('should result 3 errors', () => {
+  it('should result 2 errors', () => {
     const code = '<p TEST="abc">'
     const messages = HTMLHint.verify(code)
-    expect(messages.length).to.be(3)
+    expect(messages.length).to.be(2)
   })
 })
diff --git a/test/rules/doctype-first.spec.js b/test/rules/doctype-first.spec.js
index 630541c1f..b1831bde6 100644
--- a/test/rules/doctype-first.spec.js
+++ b/test/rules/doctype-first.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'doctype-first'
diff --git a/test/rules/doctype-html5.spec.js b/test/rules/doctype-html5.spec.js
index b796ddb28..d11570ef7 100644
--- a/test/rules/doctype-html5.spec.js
+++ b/test/rules/doctype-html5.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'doctype-html5'
diff --git a/test/rules/head-require.spec.js b/test/rules/head-require.spec.js
index 576efc041..6505f3976 100644
--- a/test/rules/head-require.spec.js
+++ b/test/rules/head-require.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'head-script-disabled'
diff --git a/test/rules/head-script-disabled.spec.js b/test/rules/head-script-disabled.spec.js
index 576efc041..6505f3976 100644
--- a/test/rules/head-script-disabled.spec.js
+++ b/test/rules/head-script-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'head-script-disabled'
diff --git a/test/rules/href-abs-or-rel.spec.js b/test/rules/href-abs-or-rel.spec.js
index 3a7420c2b..77fe35864 100644
--- a/test/rules/href-abs-or-rel.spec.js
+++ b/test/rules/href-abs-or-rel.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'href-abs-or-rel'
diff --git a/test/rules/id-class-ad-disabled.spec.js b/test/rules/id-class-ad-disabled.spec.js
index 599e2f37a..c5ea2f29a 100644
--- a/test/rules/id-class-ad-disabled.spec.js
+++ b/test/rules/id-class-ad-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'id-class-ad-disabled'
diff --git a/test/rules/id-class-value.spec.js b/test/rules/id-class-value.spec.js
index a28cce0f1..c6978bf50 100644
--- a/test/rules/id-class-value.spec.js
+++ b/test/rules/id-class-value.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'id-class-value'
diff --git a/test/rules/id-unique.spec.js b/test/rules/id-unique.spec.js
index 75fc84868..c85abc94e 100644
--- a/test/rules/id-unique.spec.js
+++ b/test/rules/id-unique.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'id-unique'
diff --git a/test/rules/inline-script-disabled.spec.js b/test/rules/inline-script-disabled.spec.js
index 869eb53c1..7a66c988d 100644
--- a/test/rules/inline-script-disabled.spec.js
+++ b/test/rules/inline-script-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'inline-script-disabled'
diff --git a/test/rules/inline-style-disabled.spec.js b/test/rules/inline-style-disabled.spec.js
index fec36f2d2..a0cb5f972 100644
--- a/test/rules/inline-style-disabled.spec.js
+++ b/test/rules/inline-style-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'inline-style-disabled'
diff --git a/test/rules/input-requires-label.spec.js b/test/rules/input-requires-label.spec.js
index 8d2637e92..d747ad9a5 100644
--- a/test/rules/input-requires-label.spec.js
+++ b/test/rules/input-requires-label.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruleId = 'input-requires-label'
diff --git a/test/rules/script-disabled.spec.js b/test/rules/script-disabled.spec.js
index 5a0ae5b07..a803c5951 100755
--- a/test/rules/script-disabled.spec.js
+++ b/test/rules/script-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'script-disabled'
diff --git a/test/rules/space-tab-mixed-disabled.spec.js b/test/rules/space-tab-mixed-disabled.spec.js
index 6542c414d..ab3621246 100644
--- a/test/rules/space-tab-mixed-disabled.spec.js
+++ b/test/rules/space-tab-mixed-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'space-tab-mixed-disabled'
diff --git a/test/rules/spec-char-escape.spec.js b/test/rules/spec-char-escape.spec.js
index b22bf84cd..fddc62df2 100644
--- a/test/rules/spec-char-escape.spec.js
+++ b/test/rules/spec-char-escape.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'spec-char-escape'
diff --git a/test/rules/src-not-empty.spec.js b/test/rules/src-not-empty.spec.js
index 895d0b352..ddbf9b655 100644
--- a/test/rules/src-not-empty.spec.js
+++ b/test/rules/src-not-empty.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'src-not-empty'
diff --git a/test/rules/style-disabled.spec.js b/test/rules/style-disabled.spec.js
index dcbc001d2..4c5ef6d55 100644
--- a/test/rules/style-disabled.spec.js
+++ b/test/rules/style-disabled.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'style-disabled'
diff --git a/test/rules/tag-pair.spec.js b/test/rules/tag-pair.spec.js
index 84dcd916b..72a99fc0e 100644
--- a/test/rules/tag-pair.spec.js
+++ b/test/rules/tag-pair.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'tag-pair'
diff --git a/test/rules/tag-self-close.spec.js b/test/rules/tag-self-close.spec.js
index a66699246..945226a96 100644
--- a/test/rules/tag-self-close.spec.js
+++ b/test/rules/tag-self-close.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'tag-self-close'
diff --git a/test/rules/tagname-lowercase.spec.js b/test/rules/tagname-lowercase.spec.js
index 0f6116f94..d1fed87fa 100644
--- a/test/rules/tagname-lowercase.spec.js
+++ b/test/rules/tagname-lowercase.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'tagname-lowercase'
diff --git a/test/rules/tagname-specialchars.spec.js b/test/rules/tagname-specialchars.spec.js
index 583f6a3ba..a9c8b1246 100644
--- a/test/rules/tagname-specialchars.spec.js
+++ b/test/rules/tagname-specialchars.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'tagname-specialchars'
diff --git a/test/rules/tags-check.spec.js b/test/rules/tags-check.spec.js
index cb20f71c0..5b66f4bb0 100644
--- a/test/rules/tags-check.spec.js
+++ b/test/rules/tags-check.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'tags-check'
diff --git a/test/rules/title-require.spec.js b/test/rules/title-require.spec.js
index 0ee456249..958f6a01d 100644
--- a/test/rules/title-require.spec.js
+++ b/test/rules/title-require.spec.js
@@ -1,5 +1,6 @@
 const expect = require('expect.js')
 
+/** @type import('../../src/core/core').HTMLHint */
 const HTMLHint = require('../../dist/htmlhint.js').HTMLHint
 
 const ruldId = 'title-require'