diff --git a/DEPS b/DEPS
index b78ac1a76884..86c2898e8dc2 100644
--- a/DEPS
+++ b/DEPS
@@ -1,7 +1,7 @@
 use_relative_paths = True
 
 deps = {
-  "vendor/adblock_rust_ffi": "https://github.com/brave/adblock-rust-ffi.git@d757c647699ff7e6dacc5d7bbd51649b509609a5",
+  "vendor/adblock_rust_ffi": "https://github.com/brave/adblock-rust-ffi.git@89127a30655eaf54cf73794309846084ea8b91b9",
   "vendor/autoplay-whitelist": "https://github.com/brave/autoplay-whitelist.git@ea527a4d36051daedb34421e129c98eda06cb5d3",
   "vendor/extension-whitelist": "https://github.com/brave/extension-whitelist.git@7843f62e26a23c51336330e220e9d7992680aae9",
   "vendor/hashset-cpp": "https://github.com/brave/hashset-cpp.git@6eab0271d014ff09bd9f38abe1e0c117e13e9aa9",
diff --git a/browser/extensions/BUILD.gn b/browser/extensions/BUILD.gn
index 0f376878c8e2..a82b196fc2fd 100644
--- a/browser/extensions/BUILD.gn
+++ b/browser/extensions/BUILD.gn
@@ -68,9 +68,7 @@ source_set("extensions") {
     "//brave/components/brave_component_updater/browser",
     "//brave/components/brave_extension:generated_resources",
     "//brave/components/brave_extension:static_resources",
-    "//brave/components/brave_shields/browser",
     "//chrome/browser/extensions",
-    "//chrome/common",
     "//components/gcm_driver:gcm_driver",
     "//components/gcm_driver:gcm_buildflags",
     "//components/prefs",
diff --git a/browser/extensions/api/brave_shields_api.cc b/browser/extensions/api/brave_shields_api.cc
index b483985bb5e8..14777de13cea 100644
--- a/browser/extensions/api/brave_shields_api.cc
+++ b/browser/extensions/api/brave_shields_api.cc
@@ -10,12 +10,10 @@
 #include <utility>
 
 #include "base/strings/string_number_conversions.h"
-#include "brave/browser/brave_browser_process_impl.h"
 #include "brave/browser/extensions/api/brave_action_api.h"
 #include "brave/browser/webcompat_reporter/webcompat_reporter_dialog.h"
 #include "brave/common/extensions/api/brave_shields.h"
 #include "brave/common/extensions/extension_constants.h"
-#include "brave/components/brave_shields/browser/ad_block_service.h"
 #include "brave/components/brave_shields/browser/brave_shields_p3a.h"
 #include "brave/components/brave_shields/browser/brave_shields_util.h"
 #include "brave/components/brave_shields/browser/brave_shields_web_contents_observer.h"
@@ -25,7 +23,6 @@
 #include "chrome/browser/extensions/chrome_extension_function_details.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
 #include "chrome/browser/profiles/profile.h"
-#include "chrome/common/chrome_features.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/extension_util.h"
 
@@ -44,40 +41,6 @@ const char kInvalidControlTypeError[] = "Invalid ControlType.";
 
 }  // namespace
 
-
-ExtensionFunction::ResponseAction
-BraveShieldsHostnameCosmeticResourcesFunction::Run() {
-  std::unique_ptr<brave_shields::HostnameCosmeticResources::Params> params(
-      brave_shields::HostnameCosmeticResources::Params::Create(*args_));
-  EXTENSION_FUNCTION_VALIDATE(params.get());
-
-  base::Optional<base::Value> resources = g_brave_browser_process->
-      ad_block_service()->HostnameCosmeticResources(params->hostname);
-
-  if (!resources || !resources->is_dict()) {
-    return RespondNow(Error(
-        "Hostname-specific cosmetic resources could not be returned"));
-  }
-  auto result_list = std::make_unique<base::ListValue>();
-
-  result_list->GetList().push_back(std::move(*resources));
-
-  return RespondNow(ArgumentList(std::move(result_list)));
-}
-
-ExtensionFunction::ResponseAction BraveShieldsClassIdStylesheetFunction::Run() {
-  std::unique_ptr<brave_shields::ClassIdStylesheet::Params> params(
-      brave_shields::ClassIdStylesheet::Params::Create(*args_));
-  EXTENSION_FUNCTION_VALIDATE(params.get());
-
-  std::string stylesheet = g_brave_browser_process->
-      ad_block_service()->ClassIdStylesheet(params->classes,
-                                            params->ids,
-                                            params->exceptions);
-  return RespondNow(OneArgument(std::make_unique<base::Value>(stylesheet)));
-}
-
-
 ExtensionFunction::ResponseAction BraveShieldsAllowScriptsOnceFunction::Run() {
   std::unique_ptr<brave_shields::AllowScriptsOnce::Params> params(
       brave_shields::AllowScriptsOnce::Params::Create(*args_));
@@ -154,14 +117,6 @@ BraveShieldsGetBraveShieldsEnabledFunction::Run() {
   return RespondNow(OneArgument(std::move(result)));
 }
 
-ExtensionFunction::ResponseAction
-BraveShieldsGetCosmeticFilteringEnabledFunction::Run() {
-  auto result = std::make_unique<base::Value>(
-      base::FeatureList::IsEnabled(features::kBraveAdblockCosmeticFiltering));
-
-  return RespondNow(OneArgument(std::move(result)));
-}
-
 ExtensionFunction::ResponseAction BraveShieldsSetAdControlTypeFunction::Run() {
   std::unique_ptr<brave_shields::SetAdControlType::Params> params(
       brave_shields::SetAdControlType::Params::Create(*args_));
diff --git a/browser/extensions/api/brave_shields_api.h b/browser/extensions/api/brave_shields_api.h
index 21a6adb36a36..017dda73446e 100644
--- a/browser/extensions/api/brave_shields_api.h
+++ b/browser/extensions/api/brave_shields_api.h
@@ -11,26 +11,6 @@
 namespace extensions {
 namespace api {
 
-class BraveShieldsHostnameCosmeticResourcesFunction : public ExtensionFunction {
- public:
-  DECLARE_EXTENSION_FUNCTION("braveShields.hostnameCosmeticResources", UNKNOWN)
-
- protected:
-  ~BraveShieldsHostnameCosmeticResourcesFunction() override {}
-
-  ResponseAction Run() override;
-};
-
-class BraveShieldsClassIdStylesheetFunction : public ExtensionFunction {
- public:
-  DECLARE_EXTENSION_FUNCTION("braveShields.classIdStylesheet", UNKNOWN)
-
- protected:
-  ~BraveShieldsClassIdStylesheetFunction() override {}
-
-  ResponseAction Run() override;
-};
-
 class BraveShieldsAllowScriptsOnceFunction : public ExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("braveShields.allowScriptsOnce", UNKNOWN)
@@ -72,18 +52,6 @@ class BraveShieldsGetBraveShieldsEnabledFunction : public ExtensionFunction {
   ResponseAction Run() override;
 };
 
-class BraveShieldsGetCosmeticFilteringEnabledFunction
-    : public ExtensionFunction {
- public:
-  DECLARE_EXTENSION_FUNCTION("braveShields.getCosmeticFilteringEnabled",
-                             UNKNOWN)
-
- protected:
-  ~BraveShieldsGetCosmeticFilteringEnabledFunction() override {}
-
-  ResponseAction Run() override;
-};
-
 class BraveShieldsSetAdControlTypeFunction : public ExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("braveShields.setAdControlType", UNKNOWN)
diff --git a/chromium_src/chrome/browser/about_flags.cc b/chromium_src/chrome/browser/about_flags.cc
index 3a6acc4a47d2..e910bb11f61f 100644
--- a/chromium_src/chrome/browser/about_flags.cc
+++ b/chromium_src/chrome/browser/about_flags.cc
@@ -3,12 +3,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#define BRAVE_FEATURE_ENTRIES \
-    {"brave-adblock-cosmetic-filtering",                                   \
-     flag_descriptions::kBraveAdblockCosmeticFilteringName,                \
-     flag_descriptions::kBraveAdblockCosmeticFilteringDescription, kOsAll, \
-     FEATURE_VALUE_TYPE(features::kBraveAdblockCosmeticFiltering)},
-
 #define SetFeatureEntryEnabled SetFeatureEntryEnabled_ChromiumImpl
 #include "../../../../chrome/browser/about_flags.cc"       // NOLINT
 #include "../../../../components/flags_ui/flags_state.cc"  // NOLINT
diff --git a/chromium_src/chrome/browser/flag_descriptions.cc b/chromium_src/chrome/browser/flag_descriptions.cc
deleted file mode 100644
index 9c63c166915d..000000000000
--- a/chromium_src/chrome/browser/flag_descriptions.cc
+++ /dev/null
@@ -1,12 +0,0 @@
-/* Copyright (c) 2019 The Brave Authors. All rights reserved.
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "../../../../chrome/browser/flag_descriptions.cc"
-
-namespace flag_descriptions {
-const char kBraveAdblockCosmeticFilteringName[] = "Enable cosmetic filtering";
-const char kBraveAdblockCosmeticFilteringDescription[] =
-    "Enable support for cosmetic filtering";
-}
diff --git a/chromium_src/chrome/browser/flag_descriptions.h b/chromium_src/chrome/browser/flag_descriptions.h
deleted file mode 100644
index dda099d1930b..000000000000
--- a/chromium_src/chrome/browser/flag_descriptions.h
+++ /dev/null
@@ -1,16 +0,0 @@
-/* Copyright (c) 2019 The Brave Authors. All rights reserved.
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef BRAVE_CHROMIUM_SRC_CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
-#define BRAVE_CHROMIUM_SRC_CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
-
-#include "../../../../chrome/browser/flag_descriptions.h"
-
-namespace flag_descriptions {
-extern const char kBraveAdblockCosmeticFilteringName[];
-extern const char kBraveAdblockCosmeticFilteringDescription[];
-}
-
-#endif  // BRAVE_CHROMIUM_SRC_CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
diff --git a/chromium_src/chrome/common/chrome_features.cc b/chromium_src/chrome/common/chrome_features.cc
deleted file mode 100644
index 6b76fbe55068..000000000000
--- a/chromium_src/chrome/common/chrome_features.cc
+++ /dev/null
@@ -1,12 +0,0 @@
-/* Copyright (c) 2019 The Brave Authors. All rights reserved.
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "../../../../chrome/common/chrome_features.cc"
-
-namespace features {
-const base::Feature kBraveAdblockCosmeticFiltering{
-    "BraveAdblockCosmeticFiltering",
-    base::FEATURE_DISABLED_BY_DEFAULT};
-}
diff --git a/chromium_src/chrome/common/chrome_features.h b/chromium_src/chrome/common/chrome_features.h
deleted file mode 100644
index b92d0084713a..000000000000
--- a/chromium_src/chrome/common/chrome_features.h
+++ /dev/null
@@ -1,16 +0,0 @@
-/* Copyright (c) 2019 The Brave Authors. All rights reserved.
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef BRAVE_CHROMIUM_SRC_CHROME_COMMON_CHROME_FEATURES_H_
-#define BRAVE_CHROMIUM_SRC_CHROME_COMMON_CHROME_FEATURES_H_
-
-#include "../../../../chrome/common/chrome_features.h"
-
-namespace features {
-COMPONENT_EXPORT(CHROME_FEATURES)
-extern const base::Feature kBraveAdblockCosmeticFiltering;
-}
-
-#endif  // BRAVE_CHROMIUM_SRC_CHROME_COMMON_CHROME_FEATURES_H_
diff --git a/common/extensions/api/brave_shields.json b/common/extensions/api/brave_shields.json
index 81ea792cb645..2f57e398a9c1 100644
--- a/common/extensions/api/brave_shields.json
+++ b/common/extensions/api/brave_shields.json
@@ -73,65 +73,6 @@
         "description": "Notifies the browser about the fact of showing the panel",
         "parameters": []
       },
-      {
-        "name": "hostnameCosmeticResources",
-        "type": "function",
-        "description": "Get a cosmetic adblocking stylesheet, generic style exceptions, and script injections specific for the given hostname and domain",
-        "parameters": [
-          {
-            "name": "hostname",
-            "type": "string"
-          },
-          {
-            "type": "function",
-            "name": "callback",
-            "parameters": [
-              {
-                "name": "hostnameSpecificResources",
-                "type": "object",
-                "properties": {
-                  "hide_selectors": {"type": "array", "items": {"type": "string"}, "description": "Hostname-specific CSS selectors that should be hidden from the page"},
-                  "style_selectors": {"type": "object", "additionalProperties": {"type": "array", "items": {"type": "string"}}, "description": "Hostname-specific CSS selectors that should be restyled, with their associated CSS style rules"},
-                  "exceptions": {"type": "array", "items": {"type": "string"}, "description": "Hostname-specific overrides for generic cosmetic blocking selectors"},
-                  "injected_script": {"type": "string", "description": "A script to inject as the page is loading"}
-                }
-              }
-            ]
-          }
-        ]
-      },
-      {
-        "name": "classIdStylesheet",
-        "type": "function",
-        "description": "Get a stylesheet of generic rules that may apply to the given set of classes and ids without any of the given excepted selectors",
-        "parameters": [
-          {
-            "name": "classes",
-            "type": "array",
-            "items": {"type": "string"}
-          },
-          {
-            "name": "ids",
-            "type": "array",
-            "items": {"type": "string"}
-          },
-          {
-            "name": "exceptions",
-            "type": "array",
-            "items": {"type": "string"}
-          },
-          {
-            "type": "function",
-            "name": "callback",
-            "parameters": [
-              {
-                "name": "stylesheet",
-                "type": "string"
-              }
-            ]
-          }
-        ]
-      },
       {
         "name": "getBraveShieldsEnabled",
         "type": "function",
@@ -153,23 +94,6 @@
           }
         ]
       },
-      {
-        "name": "getCosmeticFilteringEnabled",
-        "type": "function",
-        "description": "Get whether or not the cosmetic filtering feature flag is enabled",
-        "parameters": [
-          {
-            "type": "function",
-            "name": "callback",
-            "parameters": [
-              {
-                "name": "enabled",
-                "type": "boolean"
-              }
-            ]
-          }
-        ]
-      },
       {
         "name": "setAdControlType",
         "type": "function",
diff --git a/components/brave_extension/extension/brave_extension/BUILD.gn b/components/brave_extension/extension/brave_extension/BUILD.gn
index 2e0e84155c1e..3cdad09ed270 100644
--- a/components/brave_extension/extension/brave_extension/BUILD.gn
+++ b/components/brave_extension/extension/brave_extension/BUILD.gn
@@ -9,7 +9,6 @@ transpile_web_ui("brave_extension") {
     ["brave_extension_background", rebase_path("background.ts")],
     ["content", rebase_path("content.ts")],
     ["content_dapps", rebase_path("content_dapps.ts")],
-    ["content_cosmetic", rebase_path("content_cosmetic.ts")],
     ["webstore", rebase_path("webstore.ts")],
   ]
 
diff --git a/components/brave_extension/extension/brave_extension/actions/shieldsPanelActions.ts b/components/brave_extension/extension/brave_extension/actions/shieldsPanelActions.ts
index 2d590928b1b2..b566c3247c9d 100644
--- a/components/brave_extension/extension/brave_extension/actions/shieldsPanelActions.ts
+++ b/components/brave_extension/extension/brave_extension/actions/shieldsPanelActions.ts
@@ -137,28 +137,3 @@ export const shieldsReady: actions.ShieldsReady = () => {
     type: types.SHIELDS_READY
   }
 }
-
-export const generateClassIdStylesheet = (tabId: number, classes: string[], ids: string[]) => {
-  return {
-    type: types.GENERATE_CLASS_ID_STYLESHEET,
-    tabId,
-    classes,
-    ids
-  }
-}
-
-export const cosmeticFilterRuleExceptions = (tabId: number, exceptions: string[]) => {
-  return {
-    type: types.COSMETIC_FILTER_RULE_EXCEPTIONS,
-    tabId,
-    exceptions
-  }
-}
-
-export const contentScriptsLoaded: actions.ContentScriptsLoaded = (tabId: number, url: string) => {
-  return {
-    type: types.CONTENT_SCRIPTS_LOADED,
-    tabId,
-    url
-  }
-}
diff --git a/components/brave_extension/extension/brave_extension/background/api/cosmeticFilterAPI.ts b/components/brave_extension/extension/brave_extension/background/api/cosmeticFilterAPI.ts
index 1ee5d0efeeb7..936e1453efe6 100644
--- a/components/brave_extension/extension/brave_extension/background/api/cosmeticFilterAPI.ts
+++ b/components/brave_extension/extension/brave_extension/background/api/cosmeticFilterAPI.ts
@@ -2,34 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import shieldsPanelActions from '../actions/shieldsPanelActions'
-
-const generateCosmeticBlockingStylesheet = (hideSelectors: string[], styleSelectors: any) => {
-  let stylesheet = ''
-  if (hideSelectors.length > 0) {
-    stylesheet += hideSelectors[0]
-    for (const selector of hideSelectors.slice(1)) {
-      stylesheet += ',' + selector
-    }
-    stylesheet += '{display:none !important;}\n'
-  }
-  for (const selector in styleSelectors) {
-    stylesheet += selector + '{' + styleSelectors[selector] + '\n'
-  }
-
-  return stylesheet
-}
-
-export const injectClassIdStylesheet = (tabId: number, classes: string[], ids: string[], exceptions: string[]) => {
-  chrome.braveShields.classIdStylesheet(classes, ids, exceptions, stylesheet => {
-    chrome.tabs.insertCSS(tabId, {
-      code: stylesheet,
-      cssOrigin: 'user',
-      runAt: 'document_start'
-    })
-  })
-}
-
 export const addSiteCosmeticFilter = async (origin: string, cssfilter: string) => {
   chrome.storage.local.get('cosmeticFilterList', (storeData = {}) => {
     let storeList = Object.assign({}, storeData.cosmeticFilterList)
@@ -50,34 +22,7 @@ export const removeSiteFilter = (origin: string) => {
   })
 }
 
-export const applyAdblockCosmeticFilters = (tabId: number, hostname: string) => {
-  chrome.braveShields.hostnameCosmeticResources(hostname, async (resources) => {
-    if (chrome.runtime.lastError) {
-      console.warn('Unable to get cosmetic filter data for the current host')
-      return
-    }
-
-    const stylesheet = generateCosmeticBlockingStylesheet(resources.hide_selectors, resources.style_selectors)
-    if (stylesheet) {
-      chrome.tabs.insertCSS(tabId, {
-        code: stylesheet,
-        cssOrigin: 'user',
-        runAt: 'document_start'
-      })
-    }
-
-    if (resources.injected_script) {
-      chrome.tabs.executeScript(tabId, {
-        code: resources.injected_script,
-        runAt: 'document_start'
-      })
-    }
-
-    shieldsPanelActions.cosmeticFilterRuleExceptions(tabId, resources.exceptions)
-  })
-}
-
-export const applyCSSCosmeticFilters = (tabId: number, hostname: string) => {
+export const applySiteFilters = (tabId: number, hostname: string) => {
   chrome.storage.local.get('cosmeticFilterList', (storeData = {}) => {
     if (!storeData.cosmeticFilterList) {
       if (process.env.NODE_ENV === 'shields_development') {
diff --git a/components/brave_extension/extension/brave_extension/background/api/shieldsAPI.ts b/components/brave_extension/extension/brave_extension/background/api/shieldsAPI.ts
index 22499e17e1f9..b39824165496 100644
--- a/components/brave_extension/extension/brave_extension/background/api/shieldsAPI.ts
+++ b/components/brave_extension/extension/brave_extension/background/api/shieldsAPI.ts
@@ -27,8 +27,7 @@ export const getShieldSettingsForTabData = (tabData?: chrome.tabs.Tab) => {
     chrome.braveShields.getHTTPSEverywhereEnabledAsync(tabData.url),
     chrome.braveShields.getNoScriptControlTypeAsync(tabData.url),
     chrome.braveShields.getFingerprintingControlTypeAsync(tabData.url),
-    chrome.braveShields.getCookieControlTypeAsync(tabData.url),
-    chrome.braveShields.getCosmeticFilteringEnabledAsync()
+    chrome.braveShields.getCookieControlTypeAsync(tabData.url)
   ]).then((details) => {
     return {
       url: url.href,
@@ -41,8 +40,7 @@ export const getShieldSettingsForTabData = (tabData?: chrome.tabs.Tab) => {
       httpUpgradableResources: details[2] ? 'block' : 'allow',
       javascript: details[3],
       fingerprinting: details[4],
-      cookies: details[5],
-      cosmeticBlocking: details[6]
+      cookies: details[5]
     }
   }).catch(() => {
     return {
@@ -51,7 +49,6 @@ export const getShieldSettingsForTabData = (tabData?: chrome.tabs.Tab) => {
       hostname,
       id: tabData.id,
       braveShields: 'block',
-      cosmeticBlocking: 0,
       ads: 0,
       trackers: 0,
       httpUpgradableResources: 0,
diff --git a/components/brave_extension/extension/brave_extension/background/events/cosmeticFilterEvents.ts b/components/brave_extension/extension/brave_extension/background/events/cosmeticFilterEvents.ts
index 99b92f25eed9..9e92d5a84b10 100644
--- a/components/brave_extension/extension/brave_extension/background/events/cosmeticFilterEvents.ts
+++ b/components/brave_extension/extension/brave_extension/background/events/cosmeticFilterEvents.ts
@@ -4,7 +4,6 @@ import {
   removeSiteFilter,
   removeAllFilters
 } from '../api/cosmeticFilterAPI'
-import shieldsPanelActions from '../actions/shieldsPanelActions'
 
 export let rule = {
   host: '',
@@ -50,33 +49,6 @@ chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
       rule.host = msg.baseURI
       break
     }
-    case 'classIdStylesheet': {
-      const tab = sender.tab
-      if (tab === undefined) {
-        break
-      }
-      const tabId = tab.id
-      if (tabId === undefined) {
-        break
-      }
-      shieldsPanelActions.generateClassIdStylesheet(tabId, msg.classes, msg.ids)
-      break
-    }
-    case 'contentScriptsLoaded': {
-      const tab = sender.tab
-      if (tab === undefined) {
-        break
-      }
-      const tabId = tab.id
-      if (tabId === undefined) {
-        break
-      }
-      const url = tab.url
-      if (url === undefined) {
-        break
-      }
-      shieldsPanelActions.contentScriptsLoaded(tabId, url)
-    }
   }
 })
 
diff --git a/components/brave_extension/extension/brave_extension/background/reducers/shieldsPanelReducer.ts b/components/brave_extension/extension/brave_extension/background/reducers/shieldsPanelReducer.ts
index 8db43e0c2cfa..c0269e98a179 100644
--- a/components/brave_extension/extension/brave_extension/background/reducers/shieldsPanelReducer.ts
+++ b/components/brave_extension/extension/brave_extension/background/reducers/shieldsPanelReducer.ts
@@ -33,11 +33,7 @@ import {
   reportBrokenSite
 } from '../api/shieldsAPI'
 import { reloadTab } from '../api/tabsAPI'
-import {
-  injectClassIdStylesheet,
-  applyAdblockCosmeticFilters,
-  applyCSSCosmeticFilters
-} from '../api/cosmeticFilterAPI'
+import { applySiteFilters } from '../api/cosmeticFilterAPI'
 
 // Helpers
 import { getAllowedScriptsOrigins } from '../../helpers/noScriptUtils'
@@ -62,7 +58,7 @@ export default function shieldsPanelReducer (
         state = shieldsPanelState.resetBlockingResources(state, action.tabId)
         state = noScriptState.resetNoScriptInfo(state, action.tabId, new window.URL(action.url).origin)
       }
-      applyCSSCosmeticFilters(action.tabId, getHostname(action.url))
+      applySiteFilters(action.tabId, getHostname(action.url))
       break
     }
     case windowTypes.WINDOW_REMOVED: {
@@ -109,9 +105,6 @@ export default function shieldsPanelReducer (
     case shieldsPanelTypes.SHIELDS_PANEL_DATA_UPDATED: {
       state = shieldsPanelState.updateTabShieldsData(state, action.details.id, action.details)
       shieldsPanelState.updateShieldsIcon(state)
-      if (chrome.test && shieldsPanelState.getActiveTabData(state)) {
-        chrome.test.sendMessage('brave-extension-shields-data-ready')
-      }
       break
     }
     case shieldsPanelTypes.SHIELDS_TOGGLED: {
@@ -347,47 +340,6 @@ export default function shieldsPanelReducer (
       })
       break
     }
-    case shieldsPanelTypes.GENERATE_CLASS_ID_STYLESHEET: {
-      const tabData = state.tabs[action.tabId]
-      if (!tabData) {
-        console.error('Active tab not found')
-        break
-      }
-      const exceptions = tabData.cosmeticFilters.ruleExceptions
-
-      // setTimeout is used to prevent injectClassIdStylesheet from calling
-      // another Redux function immediately
-      setTimeout(() => injectClassIdStylesheet(action.tabId, action.classes, action.ids, exceptions), 0)
-      break
-    }
-    case shieldsPanelTypes.COSMETIC_FILTER_RULE_EXCEPTIONS: {
-      const tabData = state.tabs[action.tabId]
-      if (!tabData) {
-        console.error('Active tab not found')
-        break
-      }
-      state = shieldsPanelState.saveCosmeticFilterRuleExceptions(state, action.tabId, action.exceptions)
-      chrome.tabs.sendMessage(action.tabId, {
-        type: 'cosmeticFilterGenericExceptions'
-      })
-      break
-    }
-    case shieldsPanelTypes.CONTENT_SCRIPTS_LOADED: {
-      const tabData = state.tabs[action.tabId]
-      if (!tabData) {
-        console.error('Active tab not found')
-        break
-      }
-      const cosmeticBlockingEnabled = tabData.cosmeticBlocking
-      chrome.braveShields.getBraveShieldsEnabledAsync(action.url)
-        .then((braveShieldsEnabled: boolean) => {
-          const doCosmeticBlocking = braveShieldsEnabled && cosmeticBlockingEnabled
-          if (doCosmeticBlocking) {
-            applyAdblockCosmeticFilters(action.tabId, getHostname(action.url))
-          }
-        })
-      break
-    }
   }
 
   if (!areObjectsEqual(state.persistentData, initialPersistentData)) {
diff --git a/components/brave_extension/extension/brave_extension/constants/shieldsPanelTypes.ts b/components/brave_extension/extension/brave_extension/constants/shieldsPanelTypes.ts
index faea8d578819..0b1ee008ef0d 100644
--- a/components/brave_extension/extension/brave_extension/constants/shieldsPanelTypes.ts
+++ b/components/brave_extension/extension/brave_extension/constants/shieldsPanelTypes.ts
@@ -20,6 +20,3 @@ export const SET_FINAL_SCRIPTS_BLOCKED_ONCE_STATE = 'SET_FINAL_SCRIPTS_BLOCKED_O
 export const SET_ADVANCED_VIEW_FIRST_ACCESS = 'SET_ADVANCED_VIEW_FIRST_ACCESS'
 export const TOGGLE_ADVANCED_VIEW = 'TOGGLE_ADVANCED_VIEW'
 export const SHIELDS_READY = 'SHIELDS_READY'
-export const GENERATE_CLASS_ID_STYLESHEET = 'GENERATE_CLASS_ID_STYLESHEET'
-export const COSMETIC_FILTER_RULE_EXCEPTIONS = 'COSMETIC_FILTER_RULE_EXCEPTIONS'
-export const CONTENT_SCRIPTS_LOADED = 'CONTENT_SCRIPTS_LOADED'
diff --git a/components/brave_extension/extension/brave_extension/content.ts b/components/brave_extension/extension/brave_extension/content.ts
index 7256e7238c07..a1c3d55d2388 100644
--- a/components/brave_extension/extension/brave_extension/content.ts
+++ b/components/brave_extension/extension/brave_extension/content.ts
@@ -1,13 +1,3 @@
-// Notify the background script as soon as the content script has loaded.
-// chrome.tabs.insertCSS may sometimes fail to inject CSS in a newly navigated
-// page when using the chrome.webNavigation API.
-// See: https://bugs.chromium.org/p/chromium/issues/detail?id=331654#c15
-// The RenderView should always be ready when the content script begins, so
-// this message is used to trigger CSS insertion instead.
-chrome.runtime.sendMessage({
-  type: 'contentScriptsLoaded'
-})
-
 const unique = require('unique-selector').default
 let target: EventTarget | null
 
@@ -30,7 +20,6 @@ chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
   switch (action) {
     case 'getTargetSelector': {
       sendResponse(unique(target))
-      break
     }
   }
 })
diff --git a/components/brave_extension/extension/brave_extension/content_cosmetic.ts b/components/brave_extension/extension/brave_extension/content_cosmetic.ts
deleted file mode 100644
index 9e95a141cba8..000000000000
--- a/components/brave_extension/extension/brave_extension/content_cosmetic.ts
+++ /dev/null
@@ -1,80 +0,0 @@
-const queriedIds = new Set()
-const queriedClasses = new Set()
-const regexWhitespace = /\s/
-
-const getClassesAndIds = function (addedNodes: Element[]) {
-  const ids = []
-  const classes = []
-
-  for (const node of addedNodes) {
-    let nodeId = node.id
-    if (nodeId && nodeId.length !== 0) {
-      nodeId = nodeId.trim()
-      if (!queriedIds.has(nodeId) && nodeId.length !== 0) {
-        ids.push(nodeId)
-        queriedIds.add(nodeId)
-      }
-    }
-    let nodeClass = node.className
-    if (nodeClass && nodeClass.length !== 0 && !regexWhitespace.test(nodeClass)) {
-      if (!queriedClasses.has(nodeClass)) {
-        classes.push(nodeClass)
-        queriedClasses.add(nodeClass)
-      }
-    } else {
-      let nodeClasses = node.classList
-      if (nodeClasses) {
-        let j = nodeClasses.length
-        while (j--) {
-          const nodeClassJ = nodeClasses[j]
-          if (queriedClasses.has(nodeClassJ) === false) {
-            classes.push(nodeClassJ)
-            queriedClasses.add(nodeClassJ)
-          }
-        }
-      }
-    }
-  }
-  return { classes, ids }
-}
-
-const handleNewNodes = (newNodes: Element[]) => {
-  const { classes, ids } = getClassesAndIds(newNodes)
-  chrome.runtime.sendMessage({
-    type: 'classIdStylesheet',
-    classes,
-    ids
-  })
-}
-
-function applyCosmeticFilterMutationObserver () {
-  let targetNode = document.documentElement
-  let observer = new MutationObserver(mutations => {
-    const nodeList: Element[] = []
-    for (const mutation of mutations) {
-      for (let nodeIndex = 0; nodeIndex < mutation.addedNodes.length; nodeIndex++) {
-        nodeList.push(mutation.addedNodes[nodeIndex] as Element)
-      }
-    }
-    handleNewNodes(nodeList)
-  })
-  let observerConfig = {
-    childList: true,
-    subtree: true
-  }
-  observer.observe(targetNode, observerConfig)
-}
-
-chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
-  const action = typeof msg === 'string' ? msg : msg.type
-  switch (action) {
-    case 'cosmeticFilterGenericExceptions': {
-      let allNodes = Array.from(document.querySelectorAll('[id],[class]'))
-      handleNewNodes(allNodes)
-      applyCosmeticFilterMutationObserver()
-
-      sendResponse(null)
-      break
-    }
-  }
-})
diff --git a/components/brave_extension/extension/brave_extension/manifest.json b/components/brave_extension/extension/brave_extension/manifest.json
index 021b4ad92b1c..d651fea23591 100644
--- a/components/brave_extension/extension/brave_extension/manifest.json
+++ b/components/brave_extension/extension/brave_extension/manifest.json
@@ -28,8 +28,7 @@
         "https://*/*"
       ],
       "js": [
-        "out/content.bundle.js",
-        "out/content_cosmetic.bundle.js"
+        "out/content.bundle.js"
       ],
       "run_at": "document_start",
       "all_frames": true
diff --git a/components/brave_extension/extension/brave_extension/notes.md b/components/brave_extension/extension/brave_extension/notes.md
deleted file mode 100644
index e69de29bb2d1..000000000000
diff --git a/components/brave_extension/extension/brave_extension/state/shieldsPanelState.ts b/components/brave_extension/extension/brave_extension/state/shieldsPanelState.ts
index aa1ef65323bb..7ffedd1f8f16 100644
--- a/components/brave_extension/extension/brave_extension/state/shieldsPanelState.ts
+++ b/components/brave_extension/extension/brave_extension/state/shieldsPanelState.ts
@@ -112,12 +112,6 @@ export const updateResourceBlocked: shieldState.UpdateResourceBlocked = (state,
   return { ...state, tabs }
 }
 
-export const saveCosmeticFilterRuleExceptions: shieldState.SaveCosmeticFilterRuleExceptions = (state, tabId, exceptions) => {
-  const tabs: shieldState.Tabs = { ...state.tabs }
-  tabs[tabId] = { ...tabs[tabId], ...{ cosmeticFilters: { ...tabs[tabId].cosmeticFilters, ruleExceptions: exceptions } } }
-  return { ...state, tabs }
-}
-
 export const resetBlockingStats: shieldState.ResetBlockingStats = (state, tabId) => {
   const tabs: shieldState.Tabs = { ...state.tabs }
   tabs[tabId] = { ...tabs[tabId], ...{ adsBlocked: 0, trackersBlocked: 0, httpsRedirected: 0, javascriptBlocked: 0, fingerprintingBlocked: 0 } }
diff --git a/components/brave_extension/extension/brave_extension/types/actions/shieldsPanelActions.ts b/components/brave_extension/extension/brave_extension/types/actions/shieldsPanelActions.ts
index 3aa6f3a29e2d..ae808bae4b13 100644
--- a/components/brave_extension/extension/brave_extension/types/actions/shieldsPanelActions.ts
+++ b/components/brave_extension/extension/brave_extension/types/actions/shieldsPanelActions.ts
@@ -7,7 +7,6 @@ import { BlockTypes, BlockOptions, BlockFPOptions, BlockJSOptions, BlockCookiesO
 
 export interface ShieldDetails {
   id: number
-  cosmeticBlocking: boolean
   ads: BlockOptions
   trackers: BlockOptions
   httpUpgradableResources: BlockOptions
@@ -173,37 +172,6 @@ export interface ShieldsReady {
   (): ShieldsReadyReturn
 }
 
-interface GenerateClassIdStylesheetReturn {
-  type: types.GENERATE_CLASS_ID_STYLESHEET,
-  tabId: number,
-  classes: string[],
-  ids: string[]
-}
-
-export interface GenerateClassIdStylesheet {
-  (tabId: number, classes: string[], ids: string[]): GenerateClassIdStylesheetReturn
-}
-
-interface CosmeticFilterRuleExceptionsReturn {
-  type: types.COSMETIC_FILTER_RULE_EXCEPTIONS,
-  tabId: number,
-  exceptions: string[]
-}
-
-export interface CosmeticFilterRuleExceptions {
-  (tabId: number, exceptions: string[]): CosmeticFilterRuleExceptionsReturn
-}
-
-interface ContentScriptsLoadedReturn {
-  type: types.CONTENT_SCRIPTS_LOADED,
-  tabId: number,
-  url: string,
-}
-
-export interface ContentScriptsLoaded {
-  (tabId: number, url: string): ContentScriptsLoadedReturn
-}
-
 export type shieldPanelActions =
   ShieldsPanelDataUpdatedReturn |
   ShieldsToggledReturn |
@@ -221,7 +189,4 @@ export type shieldPanelActions =
   SetAllScriptsBlockedCurrentStateReturn |
   SetFinalScriptsBlockedStateReturn |
   SetAdvancedViewFirstAccessReturn |
-  ShieldsReadyReturn |
-  GenerateClassIdStylesheetReturn |
-  CosmeticFilterRuleExceptionsReturn |
-  ContentScriptsLoadedReturn
+  ShieldsReadyReturn
diff --git a/components/brave_extension/extension/brave_extension/types/adblock/adblockTypes.ts b/components/brave_extension/extension/brave_extension/types/adblock/adblockTypes.ts
index d8ab3dca6cf0..3503d66c956e 100644
--- a/components/brave_extension/extension/brave_extension/types/adblock/adblockTypes.ts
+++ b/components/brave_extension/extension/brave_extension/types/adblock/adblockTypes.ts
@@ -6,7 +6,3 @@ export type BlockTypes = 'ads' | 'trackers' | 'httpUpgradableResources' | 'javas
 export type BlockOptions = 'allow' | 'block'
 export type BlockFPOptions = 'allow' | 'block' | 'block_third_party'
 export type BlockCookiesOptions = 'allow' | 'block' | 'block_third_party'
-
-export interface CosmeticFilteringState {
-  ruleExceptions: Array<string>
-}
diff --git a/components/brave_extension/extension/brave_extension/types/constants/shieldsPanelTypes.ts b/components/brave_extension/extension/brave_extension/types/constants/shieldsPanelTypes.ts
index 05c2568a3cbb..646d2f97c11d 100644
--- a/components/brave_extension/extension/brave_extension/types/constants/shieldsPanelTypes.ts
+++ b/components/brave_extension/extension/brave_extension/types/constants/shieldsPanelTypes.ts
@@ -22,6 +22,3 @@ export type SET_FINAL_SCRIPTS_BLOCKED_ONCE_STATE = typeof types.SET_FINAL_SCRIPT
 export type SET_ADVANCED_VIEW_FIRST_ACCESS = typeof types.SET_ADVANCED_VIEW_FIRST_ACCESS
 export type TOGGLE_ADVANCED_VIEW = typeof types.TOGGLE_ADVANCED_VIEW
 export type SHIELDS_READY = typeof types.SHIELDS_READY
-export type GENERATE_CLASS_ID_STYLESHEET = typeof types.GENERATE_CLASS_ID_STYLESHEET
-export type COSMETIC_FILTER_RULE_EXCEPTIONS = typeof types.COSMETIC_FILTER_RULE_EXCEPTIONS
-export type CONTENT_SCRIPTS_LOADED = typeof types.CONTENT_SCRIPTS_LOADED
diff --git a/components/brave_extension/extension/brave_extension/types/state/shieldsPannelState.ts b/components/brave_extension/extension/brave_extension/types/state/shieldsPannelState.ts
index 2738c15456b2..d7e5f2012b28 100644
--- a/components/brave_extension/extension/brave_extension/types/state/shieldsPannelState.ts
+++ b/components/brave_extension/extension/brave_extension/types/state/shieldsPannelState.ts
@@ -3,11 +3,9 @@
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import { BlockOptions, BlockTypes, BlockFPOptions, BlockCookiesOptions } from '../other/blockTypes'
-import { CosmeticFilteringState } from '../adblock/adblockTypes'
 import { NoScriptInfo } from '../other/noScriptInfo'
 
 export interface Tab {
-  cosmeticBlocking: boolean
   ads: BlockOptions
   adsBlocked: number
   controlsOpen: boolean
@@ -30,7 +28,6 @@ export interface Tab {
   trackersBlockedResources: Array<string>
   httpsRedirectedResources: Array<string>
   fingerprintingBlockedResources: Array<string>
-  cosmeticFilters: CosmeticFilteringState
 }
 
 export interface Tabs {
@@ -88,10 +85,6 @@ export interface UpdateResourceBlocked {
   (state: State, tabId: number, blockType: BlockTypes, subresource: string): State
 }
 
-export interface SaveCosmeticFilterRuleExceptions {
-  (state: State, tabId: number, exceptions: Array<string>): State
-}
-
 export interface ResetBlockingStats {
   (state: State, tabId: number): State
 }
diff --git a/components/brave_shields/browser/BUILD.gn b/components/brave_shields/browser/BUILD.gn
index ae923b45a0ed..b29c3f3f2dcf 100644
--- a/components/brave_shields/browser/BUILD.gn
+++ b/components/brave_shields/browser/BUILD.gn
@@ -55,7 +55,6 @@ source_set("browser") {
   }
 
   deps = [
-    "//base",
     "//brave/components/brave_component_updater/browser",
     "//brave/components/content_settings/core/browser",
     "//brave/content:common",
diff --git a/components/brave_shields/browser/ad_block_base_service.cc b/components/brave_shields/browser/ad_block_base_service.cc
index 45bc9685444a..eb944d382fa3 100644
--- a/components/brave_shields/browser/ad_block_base_service.cc
+++ b/components/brave_shields/browser/ad_block_base_service.cc
@@ -12,7 +12,6 @@
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
-#include "base/json/json_reader.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ -196,19 +195,6 @@ bool AdBlockBaseService::TagExists(const std::string& tag) {
   return std::find(tags_.begin(), tags_.end(), tag) != tags_.end();
 }
 
-base::Optional<base::Value> AdBlockBaseService::HostnameCosmeticResources(
-        const std::string& hostname) {
-  return base::JSONReader::Read(
-          this->ad_block_client_->hostnameCosmeticResources(hostname));
-}
-
-std::string AdBlockBaseService::ClassIdStylesheet(
-        const std::vector<std::string>& classes,
-        const std::vector<std::string>& ids,
-        const std::vector<std::string>& exceptions) {
-  return this->ad_block_client_->classIdStylesheet(classes, ids, exceptions);
-}
-
 void AdBlockBaseService::GetDATFileData(const base::FilePath& dat_file_path) {
   base::PostTaskAndReplyWithResult(
       FROM_HERE, {base::ThreadPool(), base::MayBlock()},
diff --git a/components/brave_shields/browser/ad_block_base_service.h b/components/brave_shields/browser/ad_block_base_service.h
index 50f1469671f1..a8d5cbb6b8fb 100644
--- a/components/brave_shields/browser/ad_block_base_service.h
+++ b/components/brave_shields/browser/ad_block_base_service.h
@@ -16,7 +16,6 @@
 #include "base/files/file_path.h"
 #include "base/memory/weak_ptr.h"
 #include "base/sequence_checker.h"
-#include "base/values.h"
 #include "brave/components/brave_shields/browser/base_brave_shields_service.h"
 #include "brave/components/brave_component_updater/browser/dat_file_util.h"
 #include "content/public/common/resource_type.h"
@@ -47,13 +46,6 @@ class AdBlockBaseService : public BaseBraveShieldsService {
   void EnableTag(const std::string& tag, bool enabled);
   bool TagExists(const std::string& tag);
 
-  base::Optional<base::Value> HostnameCosmeticResources(
-          const std::string& hostname);
-  std::string ClassIdStylesheet(
-          const std::vector<std::string>& classes,
-          const std::vector<std::string>& ids,
-          const std::vector<std::string>& exceptions);
-
  protected:
   friend class ::AdBlockServiceTest;
   bool Init() override;
diff --git a/components/brave_shields/browser/ad_block_service_browsertest.cc b/components/brave_shields/browser/ad_block_service_browsertest.cc
index d794ad7f28c6..149fbafd8c07 100644
--- a/components/brave_shields/browser/ad_block_service_browsertest.cc
+++ b/components/brave_shields/browser/ad_block_service_browsertest.cc
@@ -19,13 +19,11 @@
 #include "brave/vendor/adblock_rust_ffi/src/wrapper.hpp"
 #include "chrome/browser/extensions/extension_browsertest.h"
 #include "chrome/browser/ui/browser.h"
-#include "chrome/common/chrome_features.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/test/browser_test_utils.h"
-#include "extensions/test/extension_test_message_listener.h"
 #include "net/dns/mock_host_resolver.h"
 
 using content::BrowserThread;
@@ -220,15 +218,6 @@ class AdBlockServiceTest : public ExtensionBrowserTest {
         base::CreateSingleThreadTaskRunner({BrowserThread::IO}).get()));
     ASSERT_TRUE(io_helper->Run());
   }
-
-  void WaitForBraveExtensionShieldsDataReady() {
-    // Sometimes, the page can start loading before the Shields panel has
-    // received information about the window and tab it's loaded in.
-    ExtensionTestMessageListener extension_listener(
-        "brave-extension-shields-data-ready",
-        false);
-    ASSERT_TRUE(extension_listener.WaitUntilSatisfied());
-  }
 };
 
 // Load a page with an ad image, and make sure it is blocked.
@@ -785,172 +774,3 @@ IN_PROC_BROWSER_TEST_F(AdBlockServiceTest, RedirectRulesAreRespected) {
   EXPECT_TRUE(as_expected);
   EXPECT_EQ(browser()->profile()->GetPrefs()->GetUint64(kAdsBlocked), 1ULL);
 }
-
-class CosmeticFilteringEnabledTest : public AdBlockServiceTest {
- public:
-  CosmeticFilteringEnabledTest() {
-    feature_list_.InitAndEnableFeature(
-            features::kBraveAdblockCosmeticFiltering);
-  }
-
- private:
-  base::test::ScopedFeatureList feature_list_;
-};
-
-// Ensure no cosmetic filtering occurs when the feature flag has not been
-// enabled
-IN_PROC_BROWSER_TEST_F(AdBlockServiceTest, CosmeticFilteringSimple) {
-  UpdateAdBlockInstanceWithRules(
-      "b.com###ad-banner\n"
-      "##.ad");
-
-  WaitForBraveExtensionShieldsDataReady();
-
-  GURL tab_url = embedded_test_server()->GetURL("b.com",
-                                                "/cosmetic_filtering.html");
-  ui_test_utils::NavigateToURL(browser(), tab_url);
-
-  content::WebContents* contents =
-    browser()->tab_strip_model()->GetActiveWebContents();
-
-  bool as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('#ad-banner', 'display', 'block')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-
-  as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.ad-banner', 'display', 'block')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-
-  as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.ad', 'display', 'block')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-}
-
-// Test simple cosmetic filtering
-IN_PROC_BROWSER_TEST_F(CosmeticFilteringEnabledTest, CosmeticFilteringSimple) {
-  UpdateAdBlockInstanceWithRules(
-      "b.com###ad-banner\n"
-      "##.ad");
-
-  WaitForBraveExtensionShieldsDataReady();
-
-  GURL tab_url = embedded_test_server()->GetURL("b.com",
-                                                "/cosmetic_filtering.html");
-  ui_test_utils::NavigateToURL(browser(), tab_url);
-
-  content::WebContents* contents =
-    browser()->tab_strip_model()->GetActiveWebContents();
-
-  bool as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('#ad-banner', 'display', 'none')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-
-  as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.ad-banner', 'display', 'block')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-
-  as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.ad', 'display', 'none')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-}
-
-// Test cosmetic filtering on elements added dynamically
-IN_PROC_BROWSER_TEST_F(CosmeticFilteringEnabledTest, CosmeticFilteringDynamic) {
-  UpdateAdBlockInstanceWithRules("##.blockme");
-
-  WaitForBraveExtensionShieldsDataReady();
-
-  GURL tab_url = embedded_test_server()->GetURL("b.com",
-                                                "/cosmetic_filtering.html");
-  ui_test_utils::NavigateToURL(browser(), tab_url);
-
-  content::WebContents* contents =
-    browser()->tab_strip_model()->GetActiveWebContents();
-
-  bool as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "addElementsDynamically();\n"
-              "checkSelector('.blockme', 'display', 'none')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-
-  as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.dontblockme', 'display', 'block')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-}
-
-// Test custom style rules
-IN_PROC_BROWSER_TEST_F(CosmeticFilteringEnabledTest,
-                       CosmeticFilteringCustomStyle) {
-  UpdateAdBlockInstanceWithRules("b.com##.ad:style(padding-bottom: 10px)");
-
-  WaitForBraveExtensionShieldsDataReady();
-
-  GURL tab_url = embedded_test_server()->GetURL("b.com",
-                                                "/cosmetic_filtering.html");
-  ui_test_utils::NavigateToURL(browser(), tab_url);
-
-  content::WebContents* contents =
-    browser()->tab_strip_model()->GetActiveWebContents();
-
-  bool as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.ad', 'padding-bottom', '10px')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-}
-
-// Test rules overridden by hostname-specific exception rules
-IN_PROC_BROWSER_TEST_F(CosmeticFilteringEnabledTest, CosmeticFilteringUnhide) {
-  UpdateAdBlockInstanceWithRules(
-      "##.ad\n"
-      "b.com#@#.ad\n"
-      "###ad-banner\n"
-      "a.com#@##ad-banner");
-
-  WaitForBraveExtensionShieldsDataReady();
-
-  GURL tab_url = embedded_test_server()->GetURL("b.com",
-                                                "/cosmetic_filtering.html");
-  ui_test_utils::NavigateToURL(browser(), tab_url);
-
-  content::WebContents* contents =
-    browser()->tab_strip_model()->GetActiveWebContents();
-
-  bool as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('.ad', 'display', 'block')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-
-  as_expected = false;
-  ASSERT_TRUE(ExecuteScriptAndExtractBool(
-              contents,
-              "checkSelector('#ad-banner', 'display', 'none')",
-              &as_expected));
-  EXPECT_TRUE(as_expected);
-}
diff --git a/components/definitions/chromel.d.ts b/components/definitions/chromel.d.ts
index 9b63519a12d6..55dac044620c 100644
--- a/components/definitions/chromel.d.ts
+++ b/components/definitions/chromel.d.ts
@@ -203,7 +203,6 @@ declare namespace chrome.braveShields {
   const allowScriptsOnce: any
   const setBraveShieldsEnabledAsync: any
   const getBraveShieldsEnabledAsync: any
-  const getCosmeticFilteringEnabledAsync: any
   const setAdControlTypeAsync: any
   const getAdControlTypeAsync: any
   const setCookieControlTypeAsync: any
@@ -217,15 +216,6 @@ declare namespace chrome.braveShields {
   const onShieldsPanelShown: any
   const reportBrokenSite: any
 
-  interface HostnameSpecificResources {
-    hide_selectors: string[]
-    style_selectors: any
-    exceptions: string[]
-    injected_script: string
-  }
-  const hostnameCosmeticResources: (hostname: string, callback: (resources: HostnameSpecificResources) => void) => void
-  const classIdStylesheet: (classes: string[], ids: string[], exceptions: string[], callback: (stylesheet: string) => void) => void
-
   type BraveShieldsViewPreferences = {
     showAdvancedView: boolean
   }
diff --git a/components/test/brave_extension/background/api/cosmeticFilterAPI_test.ts b/components/test/brave_extension/background/api/cosmeticFilterAPI_test.ts
index 80edf765018b..9d9bfdeeaa21 100644
--- a/components/test/brave_extension/background/api/cosmeticFilterAPI_test.ts
+++ b/components/test/brave_extension/background/api/cosmeticFilterAPI_test.ts
@@ -177,7 +177,7 @@ describe('cosmeticFilter API', () => {
       })
     })
   })
-  describe('applyCSSCosmeticFilters', () => {
+  describe('applySiteFilters', () => {
     const filter = '#cssFilter'
     const filter2 = '#cssFilter2'
 
@@ -206,7 +206,7 @@ describe('cosmeticFilter API', () => {
           'brave.com': [filter]
         }
       })
-      cosmeticFilterAPI.applyCSSCosmeticFilters(1, 'brave.com')
+      cosmeticFilterAPI.applySiteFilters(1, 'brave.com')
       expect(insertCSSStub.getCall(0).args[0]).toEqual(1)
       expect(insertCSSStub.getCall(0).args[1]).toEqual({
         code: `${filter} {display: none !important;}`,
@@ -220,7 +220,7 @@ describe('cosmeticFilter API', () => {
           'brave.com': [filter, filter2]
         }
       })
-      cosmeticFilterAPI.applyCSSCosmeticFilters(1, 'brave.com')
+      cosmeticFilterAPI.applySiteFilters(1, 'brave.com')
       expect(insertCSSStub.getCall(0).args[0]).toEqual(1)
       expect(insertCSSStub.getCall(0).args[1]).toEqual({
         code: `${filter } {display: none !important;}`,
@@ -239,7 +239,7 @@ describe('cosmeticFilter API', () => {
       getStorageStub.yields({
         cosmeticFilterList: {}
       })
-      cosmeticFilterAPI.applyCSSCosmeticFilters(1, 'brave.com')
+      cosmeticFilterAPI.applySiteFilters(1, 'brave.com')
       expect(insertCSSStub.called).toBe(false)
     })
     it('doesn\'t apply filters if storage is explicitly undefined', () => {
@@ -248,7 +248,7 @@ describe('cosmeticFilter API', () => {
           'brave.com': undefined
         }
       })
-      cosmeticFilterAPI.applyCSSCosmeticFilters(1, 'brave.com')
+      cosmeticFilterAPI.applySiteFilters(1, 'brave.com')
       expect(insertCSSStub.called).toBe(false)
     })
   })
diff --git a/components/test/brave_extension/background/api/shieldsAPI_test.ts b/components/test/brave_extension/background/api/shieldsAPI_test.ts
index 1dace3e64ec6..88cf7b8ed2ac 100644
--- a/components/test/brave_extension/background/api/shieldsAPI_test.ts
+++ b/components/test/brave_extension/background/api/shieldsAPI_test.ts
@@ -38,7 +38,6 @@ describe('Shields API', () => {
           origin: 'https://www.brave.com',
           hostname: 'www.brave.com',
           braveShields: 'block',
-          cosmeticBlocking: true,
           ads: 'block',
           trackers: 'block',
           httpUpgradableResources: 'block',
@@ -95,7 +94,6 @@ describe('Shields API', () => {
     })
     it('resolves and calls requestShieldPanelData', (cb) => {
       const details: ShieldDetails = {
-        cosmeticBlocking: true,
         ads: 'block',
         trackers: 'block',
         httpUpgradableResources: 'block',
diff --git a/components/test/testData.ts b/components/test/testData.ts
index f1cfd027cd9c..9ca1cc7307fe 100644
--- a/components/test/testData.ts
+++ b/components/test/testData.ts
@@ -217,9 +217,6 @@ export const getMockChrome = () => {
       getBraveShieldsEnabledAsync: function (url: string) {
         return Promise.resolve(false)
       },
-      getCosmeticFilteringEnabledAsync: function (url: string) {
-        return Promise.resolve(true)
-      },
       getAdControlTypeAsync: function (url: string) {
         return Promise.resolve('block')
       },
diff --git a/patches/chrome-browser-about_flags.cc.patch b/patches/chrome-browser-about_flags.cc.patch
index 322a62508e4e..5a17a14d415d 100644
--- a/patches/chrome-browser-about_flags.cc.patch
+++ b/patches/chrome-browser-about_flags.cc.patch
@@ -21,11 +21,3 @@ index 0ab55be2f96853137cec8928621360e9f639b467..34e01378c8e413af12399bc3ca30188b
  
  const FeatureEntry::Choice kPassiveListenersChoices[] = {
      {flags_ui::kGenericExperimentChoiceDefault, "", ""},
-@@ -4688,6 +4688,7 @@ const FeatureEntry kFeatureEntries[] = {
-     // "LoginCustomFlags" in tools/metrics/histograms/enums.xml. See "Flag
-     // Histograms" in tools/metrics/histograms/README.md (run the
-     // AboutFlagsHistogramTest unit test to verify this process).
-+    BRAVE_FEATURE_ENTRIES
- };
- 
- class FlagsStateSingleton {
diff --git a/test/data/cosmetic_filtering.html b/test/data/cosmetic_filtering.html
deleted file mode 100644
index 5805241e1466..000000000000
--- a/test/data/cosmetic_filtering.html
+++ /dev/null
@@ -1,41 +0,0 @@
-<html>
-<head>
-<script>
-
-function addElementsDynamically() {
-  let root = document.documentElement;
-  for (let i = 0; i < 10; i++) {
-    const e = document.createElement('div')
-    e.className = 'blockme'
-    root.appendChild(e);
-  }
-
-  for (let i = 0; i < 10; i++) {
-    const e = document.createElement('div')
-    e.className = 'dontblockme'
-    root.appendChild(e);
-  }
-}
-
-function checkSelector(selector, property, expected) {
-  setTimeout(() => {
-    let elements = [].slice.call(document.querySelectorAll(selector));
-    let result = elements.every(e => {
-      let style = window.getComputedStyle(e);
-      return style[property] === expected;
-    })
-    window.domAutomationController.send(result)
-  }, 1500)
-}
-
-</script>
-</head>
-<body>
-    <div id="ad-banner"></div>
-    <div class="ad-banner">
-        <div class="ad"></div>
-    </div>
-    <div class="ad"></div>
-    <div class="ad"></div>
-</body>
-</html>