diff --git a/.eslintrc.json b/.eslintrc.json
index 5ba83e79..3293f472 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -23,6 +23,7 @@
         "curly": [2, "multi-line"],
         "no-else-return": 2,
 
+        "node/no-missing-import": 0,
         "node/no-unsupported-features/es-syntax": 0
     },
     "overrides": [
diff --git a/package.json b/package.json
index c3889950..d2bec4a0 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,17 @@
     },
     "main": "lib/index.js",
     "types": "lib/index.d.ts",
+    "module": "lib/esm/index.js",
+    "exports": {
+        ".": {
+            "require": "./lib/index.js",
+            "import": "./lib/esm/index.js"
+        },
+        "./lib/decode.js": {
+            "require": "./lib/decode.js",
+            "import": "./lib/esm/decode.js"
+        }
+    },
     "files": [
         "lib/**/*"
     ],
@@ -48,7 +59,10 @@
         "format:es": "npm run lint:es -- --fix",
         "format:prettier": "npm run prettier -- --write",
         "prettier": "prettier '**/*.{ts,md,json,yml}'",
-        "build": "tsc && cp -r src/maps lib",
+        "build": "npm run build:cjs && npm run build:esm",
+        "build:cjs": "tsc && cp -r src/maps lib",
+        "build:esm": "tsc --module esnext --target es2019 --outDir lib/esm && npm rum build:esm:fixup && echo '{\"type\":\"module\"}' > lib/esm/package.json",
+        "build:esm:fixup": "sed -i.b '1s|\".*json\"|\"../maps/entities-encode.json\" assert {type:\"json\"}|' lib/esm/encode-trie.js && rm lib/esm/encode-trie.js.b",
         "build:docs": "typedoc --hideGenerator src/index.ts",
         "build:trie": "ts-node scripts/write-decode-map.ts",
         "build:encode-map": "jq -c 'to_entries | reverse | map( {(.value) : .key } ) | sort | add' maps/entities.json > src/maps/entities-encode.json",
@@ -62,7 +76,10 @@
     "jest": {
         "preset": "ts-jest",
         "testEnvironment": "node",
-        "coverageProvider": "v8"
+        "coverageProvider": "v8",
+        "moduleNameMapper": {
+            "^(.*)\\.js$": "$1"
+        }
     },
     "prettier": {
         "tabWidth": 4,
diff --git a/scripts/trie/encode-trie.spec.ts b/scripts/trie/encode-trie.spec.ts
index 0a8250f1..c3185167 100644
--- a/scripts/trie/encode-trie.spec.ts
+++ b/scripts/trie/encode-trie.spec.ts
@@ -1,5 +1,5 @@
-import { encodeTrie } from "./encode-trie";
-import type { TrieNode } from "./trie";
+import { encodeTrie } from "./encode-trie.js";
+import type { TrieNode } from "./trie.js";
 
 describe("encode_trie", () => {
     it("should encode an empty node", () => {
diff --git a/scripts/trie/encode-trie.ts b/scripts/trie/encode-trie.ts
index 7b690b4f..2ea88325 100644
--- a/scripts/trie/encode-trie.ts
+++ b/scripts/trie/encode-trie.ts
@@ -1,7 +1,7 @@
 /* eslint-disable node/no-unsupported-features/es-builtins */
 
 import * as assert from "assert";
-import { TrieNode } from "./trie";
+import { TrieNode } from "./trie.js";
 
 function binaryLength(num: number) {
     return Math.ceil(Math.log2(num));
diff --git a/scripts/trie/utils.ts b/scripts/trie/utils.ts
index 37a6f4ca..d679e8af 100644
--- a/scripts/trie/utils.ts
+++ b/scripts/trie/utils.ts
@@ -1,6 +1,6 @@
-import { getTrie, TrieNode } from "./trie";
-import { encodeTrie } from "./encode-trie";
-import { BinTrieFlags } from "../../src/decode";
+import { getTrie, TrieNode } from "./trie.js";
+import { encodeTrie } from "./encode-trie.js";
+import { BinTrieFlags } from "../../src/decode.js";
 import xmlMap from "../../maps/xml.json";
 
 /**
diff --git a/scripts/write-decode-map.ts b/scripts/write-decode-map.ts
index 08dbc408..75cdaa0a 100644
--- a/scripts/write-decode-map.ts
+++ b/scripts/write-decode-map.ts
@@ -3,8 +3,8 @@ import entityMap from "../maps/entities.json";
 import legacyMap from "../maps/legacy.json";
 import xmlMap from "../maps/xml.json";
 
-import { getTrie } from "./trie/trie";
-import { encodeTrie } from "./trie/encode-trie";
+import { getTrie } from "./trie/trie.js";
+import { encodeTrie } from "./trie/encode-trie.js";
 
 function convertMapToBinaryTrie(
     name: string,
diff --git a/src/decode.spec.ts b/src/decode.spec.ts
index 04d99fe9..e0eaa729 100644
--- a/src/decode.spec.ts
+++ b/src/decode.spec.ts
@@ -1,4 +1,4 @@
-import * as entities from "./decode";
+import * as entities from "./decode.js";
 
 describe("Decode test", () => {
     const testcases = [
diff --git a/src/decode.ts b/src/decode.ts
index 3b6d3bbd..36e409d1 100644
--- a/src/decode.ts
+++ b/src/decode.ts
@@ -1,9 +1,9 @@
-import htmlDecodeTree from "./generated/decode-data-html";
-import xmlDecodeTree from "./generated/decode-data-xml";
-import decodeCodePoint from "./decode_codepoint";
+import htmlDecodeTree from "./generated/decode-data-html.js";
+import xmlDecodeTree from "./generated/decode-data-xml.js";
+import decodeCodePoint from "./decode_codepoint.js";
 
 // Re-export for use by eg. htmlparser2
-export { htmlDecodeTree, xmlDecodeTree };
+export { htmlDecodeTree, xmlDecodeTree, decodeCodePoint };
 
 const enum CharCodes {
     NUM = 35, // "#"
diff --git a/src/encode.ts b/src/encode.ts
index 66defd8d..c872a712 100644
--- a/src/encode.ts
+++ b/src/encode.ts
@@ -1,4 +1,4 @@
-import { encodeHTMLTrieRe, getCodePoint } from "./encode-trie";
+import { encodeHTMLTrieRe, getCodePoint } from "./encode-trie.js";
 
 const htmlReplacer = /[\t\n!-,./:-@[-`\f{-}$\x80-\uFFFF]/g;
 const xmlReplacer = /["&'<>$\x80-\uFFFF]/g;
diff --git a/src/index.ts b/src/index.ts
index 1978c15e..16912ada 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,4 @@
-import { decodeXML, decodeHTML, decodeHTMLStrict } from "./decode";
+import { decodeXML, decodeHTML, decodeHTMLStrict } from "./decode.js";
 import {
     encodeXML,
     escapeUTF8,
@@ -6,7 +6,7 @@ import {
     encodeNonAsciiHTML,
     escapeAttribute,
     escapeText,
-} from "./encode";
+} from "./encode.js";
 
 /** The level of entities to support. */
 export enum EntityLevel {
@@ -174,7 +174,7 @@ export {
     // Legacy aliases (deprecated)
     encodeHTML as encodeHTML4,
     encodeHTML as encodeHTML5,
-} from "./encode";
+} from "./encode.js";
 
 export {
     decodeXML,
@@ -186,4 +186,4 @@ export {
     decodeHTMLStrict as decodeHTML4Strict,
     decodeHTMLStrict as decodeHTML5Strict,
     decodeXML as decodeXMLStrict,
-} from "./decode";
+} from "./decode.js";
diff --git a/tsconfig.json b/tsconfig.json
index 55c02961..62861a08 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,7 +6,7 @@
         // "lib": [],                             /* Specify library files to be included in the compilation. */
         "declaration": true /* Generates corresponding '.d.ts' file. */,
         "declarationMap": true /* Generates a sourcemap for each corresponding '.d.ts' file. */,
-        // "sourceMap": true,                     /* Generates corresponding '.map' file. */
+        "sourceMap": true /* Generates corresponding '.map' file. */,
         "outDir": "lib" /* Redirect output structure to the directory. */,
         // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
 
@@ -22,6 +22,7 @@
         /* Module Resolution Options */
         // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
         "esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */,
+        "moduleResolution": "node",
         "resolveJsonModule": true
     },
     "include": ["src"],