diff --git a/argos/playwright.config.ts b/argos/playwright.config.ts
index 31409769110c2..519227c75121b 100644
--- a/argos/playwright.config.ts
+++ b/argos/playwright.config.ts
@@ -14,6 +14,8 @@ import type {PlaywrightTestConfig} from '@playwright/test';
 const config: PlaywrightTestConfig = {
   testDir: './tests',
 
+  timeout: 60000,
+
   reporter: [['list'], ['@argos-ci/playwright/reporter']],
 
   // Run website production built
diff --git a/argos/tests/screenshot.spec.ts b/argos/tests/screenshot.spec.ts
index 70bee2af15c35..f6829a13a9d25 100644
--- a/argos/tests/screenshot.spec.ts
+++ b/argos/tests/screenshot.spec.ts
@@ -36,8 +36,12 @@ function isBlacklisted(pathname: string) {
   }
   // Some paths explicitly blacklisted
   const BlacklistedPathnames: string[] = [
-    '/feature-requests', // Flaky because of Canny widget
-    '/community/canary', // Flaky because of dynamic canary version fetched from npm
+    // Flaky because of Canny widget
+    '/feature-requests',
+    // Flaky because of dynamic canary version fetched from npm
+    '/community/canary',
+    // Long blog post with many image carousels, often timeouts
+    '/blog/2022/08/01/announcing-docusaurus-2.0',
   ];
 
   return (
diff --git a/packages/docusaurus-mdx-loader/src/loader.ts b/packages/docusaurus-mdx-loader/src/loader.ts
index 519b5da3b9cdc..a475220cd5c63 100644
--- a/packages/docusaurus-mdx-loader/src/loader.ts
+++ b/packages/docusaurus-mdx-loader/src/loader.ts
@@ -11,6 +11,7 @@ import {
   parseFrontMatter,
   escapePath,
   getFileLoaderUtils,
+  getWebpackLoaderCompilerName,
 } from '@docusaurus/utils';
 import stringifyObject from 'stringify-object';
 import preprocessor from './preprocessor';
@@ -134,10 +135,12 @@ export async function mdxLoader(
   this: LoaderContext<Options>,
   fileString: string,
 ): Promise<void> {
+  const compilerName = getWebpackLoaderCompilerName(this);
   const callback = this.async();
   const filePath = this.resourcePath;
   const reqOptions: Options = this.getOptions();
   const {query} = this;
+
   ensureMarkdownConfig(reqOptions);
 
   const {frontMatter} = parseFrontMatter(fileString);
@@ -165,6 +168,7 @@ export async function mdxLoader(
       content: preprocessedContent,
       filePath,
       frontMatter,
+      compilerName,
     });
   } catch (errorUnknown) {
     const error = errorUnknown as Error;
diff --git a/packages/docusaurus-mdx-loader/src/processor.ts b/packages/docusaurus-mdx-loader/src/processor.ts
index b7d500c64a0d0..032cdf4e2ff5f 100644
--- a/packages/docusaurus-mdx-loader/src/processor.ts
+++ b/packages/docusaurus-mdx-loader/src/processor.ts
@@ -15,8 +15,10 @@ import details from './remark/details';
 import head from './remark/head';
 import mermaid from './remark/mermaid';
 import transformAdmonitions from './remark/admonitions';
+import unusedDirectivesWarning from './remark/unusedDirectives';
 import codeCompatPlugin from './remark/mdx1Compat/codeCompatPlugin';
 import {getFormat} from './format';
+import type {WebpackCompilerName} from '@docusaurus/utils';
 import type {MDXFrontMatter} from './frontMatter';
 import type {Options} from './loader';
 import type {AdmonitionOptions} from './remark/admonitions';
@@ -37,10 +39,12 @@ type SimpleProcessor = {
     content,
     filePath,
     frontMatter,
+    compilerName,
   }: {
     content: string;
     filePath: string;
     frontMatter: {[key: string]: unknown};
+    compilerName: WebpackCompilerName;
   }) => Promise<SimpleProcessorResult>;
 };
 
@@ -123,6 +127,7 @@ async function createProcessorFactory() {
       gfm,
       options.markdownConfig.mdx1Compat.comments ? comment : null,
       ...(options.remarkPlugins ?? []),
+      unusedDirectivesWarning,
     ].filter((plugin): plugin is MDXPlugin => Boolean(plugin));
 
     // codeCompatPlugin needs to be applied last after user-provided plugins
@@ -167,12 +172,13 @@ async function createProcessorFactory() {
     });
 
     return {
-      process: async ({content, filePath, frontMatter}) => {
+      process: async ({content, filePath, frontMatter, compilerName}) => {
         const vfile = new VFile({
           value: content,
           path: filePath,
           data: {
             frontMatter,
+            compilerName,
           },
         });
         return mdxProcessor.process(vfile).then((result) => ({
diff --git a/packages/docusaurus-mdx-loader/src/remark/contentTitle/index.ts b/packages/docusaurus-mdx-loader/src/remark/contentTitle/index.ts
index e2e9977dad923..c26bd1f0cce66 100644
--- a/packages/docusaurus-mdx-loader/src/remark/contentTitle/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/contentTitle/index.ts
@@ -35,6 +35,7 @@ const plugin: Plugin = function plugin(
     const {toString} = await import('mdast-util-to-string');
     visit(root, 'heading', (headingNode: Heading, index, parent) => {
       if (headingNode.depth === 1) {
+        vfile.data.compilerName;
         vfile.data.contentTitle = toString(headingNode);
         if (removeContentTitle) {
           parent!.children.splice(index, 1);
diff --git a/packages/docusaurus-mdx-loader/src/remark/mermaid/index.ts b/packages/docusaurus-mdx-loader/src/remark/mermaid/index.ts
index 7947d3387e1f9..7a5eac045601c 100644
--- a/packages/docusaurus-mdx-loader/src/remark/mermaid/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/mermaid/index.ts
@@ -6,6 +6,8 @@
  */
 
 import visit from 'unist-util-visit';
+import {transformNode} from '../utils';
+
 // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
 import type {Transformer} from 'unified';
 import type {Code} from 'mdast';
@@ -16,10 +18,10 @@ import type {Code} from 'mdast';
 // by theme-mermaid itself
 export default function plugin(): Transformer {
   return (root) => {
-    visit(root, 'code', (node: Code, index, parent) => {
+    visit(root, 'code', (node: Code) => {
       if (node.lang === 'mermaid') {
         // TODO migrate to mdxJsxFlowElement? cf admonitions
-        parent!.children.splice(index, 1, {
+        transformNode(node, {
           type: 'mermaidCodeBlock',
           data: {
             hName: 'mermaid',
diff --git a/packages/docusaurus-mdx-loader/src/remark/transformImage/index.ts b/packages/docusaurus-mdx-loader/src/remark/transformImage/index.ts
index 5bd9c1d9a9915..956de8a8df477 100644
--- a/packages/docusaurus-mdx-loader/src/remark/transformImage/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/transformImage/index.ts
@@ -20,7 +20,7 @@ import visit from 'unist-util-visit';
 import escapeHtml from 'escape-html';
 import sizeOf from 'image-size';
 import logger from '@docusaurus/logger';
-import {assetRequireAttributeValue} from '../utils';
+import {assetRequireAttributeValue, transformNode} from '../utils';
 // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
 import type {Transformer} from 'unified';
 // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
@@ -110,14 +110,12 @@ ${(err as Error).message}`;
     }
   }
 
-  Object.keys(jsxNode).forEach(
-    (key) => delete jsxNode[key as keyof typeof jsxNode],
-  );
-
-  jsxNode.type = 'mdxJsxTextElement';
-  jsxNode.name = 'img';
-  jsxNode.attributes = attributes;
-  jsxNode.children = [];
+  transformNode(jsxNode, {
+    type: 'mdxJsxTextElement',
+    name: 'img',
+    attributes,
+    children: [],
+  });
 }
 
 async function ensureImageFileExist(imagePath: string, sourceFilePath: string) {
diff --git a/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts b/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts
index 71086023345ce..bddf42613f4f3 100644
--- a/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/transformLinks/index.ts
@@ -17,7 +17,7 @@ import {
 } from '@docusaurus/utils';
 import visit from 'unist-util-visit';
 import escapeHtml from 'escape-html';
-import {assetRequireAttributeValue} from '../utils';
+import {assetRequireAttributeValue, transformNode} from '../utils';
 // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
 import type {Transformer} from 'unified';
 // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
@@ -90,14 +90,12 @@ async function toAssetRequireNode(
 
   const {children} = node;
 
-  Object.keys(jsxNode).forEach(
-    (key) => delete jsxNode[key as keyof typeof jsxNode],
-  );
-
-  jsxNode.type = 'mdxJsxTextElement';
-  jsxNode.name = 'a';
-  jsxNode.attributes = attributes;
-  jsxNode.children = children;
+  transformNode(jsxNode, {
+    type: 'mdxJsxTextElement',
+    name: 'a',
+    attributes,
+    children,
+  });
 }
 
 async function ensureAssetFileExist(assetPath: string, sourceFilePath: string) {
diff --git a/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/containerDirectives.md b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/containerDirectives.md
new file mode 100644
index 0000000000000..2a416f0ca72bc
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/containerDirectives.md
@@ -0,0 +1,19 @@
+:::danger
+
+Take care of snowstorms...
+
+:::
+
+:::unusedDirective
+
+unused directive content
+
+:::
+
+:::NotAContainerDirective with a phrase after
+
+:::
+
+Phrase before :::NotAContainerDirective
+
+:::
diff --git a/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/leafDirectives.md b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/leafDirectives.md
new file mode 100644
index 0000000000000..73fd60c77b676
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/leafDirectives.md
@@ -0,0 +1,5 @@
+::unusedLeafDirective
+
+Leaf directive in a phrase ::NotALeafDirective
+
+::NotALeafDirective with a phrase after
diff --git a/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/textDirectives.md b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/textDirectives.md
new file mode 100644
index 0000000000000..9410feb923bec
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/textDirectives.md
@@ -0,0 +1,17 @@
+Simple: textDirective1
+
+```sh
+Simple: textDirectiveCode
+```
+
+Simple:textDirective2
+
+Simple:textDirective3[label]
+
+Simple:textDirective4{age=42}
+
+Simple:textDirective5
+
+```sh
+Simple:textDirectiveCode
+```
diff --git a/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__snapshots__/index.test.ts.snap b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__snapshots__/index.test.ts.snap
new file mode 100644
index 0000000000000..46285b8894e14
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__snapshots__/index.test.ts.snap
@@ -0,0 +1,86 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`directives remark plugin - client compiler default behavior for container directives: console 1`] = `
+[
+  [
+    "[WARNING] Docusaurus found 1 unused Markdown directives in file "packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/containerDirectives.md"
+- :::unusedDirective (7:1)
+Your content might render in an unexpected way. Visit https://github.com/facebook/docusaurus/pull/9394 to find out why and how to fix it.",
+  ],
+]
+`;
+
+exports[`directives remark plugin - client compiler default behavior for container directives: result 1`] = `
+"<admonition type="danger"><p>Take care of snowstorms...</p></admonition>
+<div><p>unused directive content</p></div>
+<p>:::NotAContainerDirective with a phrase after</p>
+<p>:::</p>
+<p>Phrase before :::NotAContainerDirective</p>
+<p>:::</p>"
+`;
+
+exports[`directives remark plugin - client compiler default behavior for leaf directives: console 1`] = `
+[
+  [
+    "[WARNING] Docusaurus found 1 unused Markdown directives in file "packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/leafDirectives.md"
+- ::unusedLeafDirective (1:1)
+Your content might render in an unexpected way. Visit https://github.com/facebook/docusaurus/pull/9394 to find out why and how to fix it.",
+  ],
+]
+`;
+
+exports[`directives remark plugin - client compiler default behavior for leaf directives: result 1`] = `
+"<div></div>
+<p>Leaf directive in a phrase ::NotALeafDirective</p>
+<p>::NotALeafDirective with a phrase after</p>"
+`;
+
+exports[`directives remark plugin - client compiler default behavior for text directives: console 1`] = `
+[
+  [
+    "[WARNING] Docusaurus found 2 unused Markdown directives in file "packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/__fixtures__/textDirectives.md"
+- :textDirective3 (9:7)
+- :textDirective4 (11:7)
+Your content might render in an unexpected way. Visit https://github.com/facebook/docusaurus/pull/9394 to find out why and how to fix it.",
+  ],
+]
+`;
+
+exports[`directives remark plugin - client compiler default behavior for text directives: result 1`] = `
+"<p>Simple: textDirective1</p>
+<pre><code class="language-sh">Simple: textDirectiveCode
+</code></pre>
+<p>Simple:textDirective2</p>
+<p>Simple<div>label</div></p>
+<p>Simple<div></div></p>
+<p>Simple:textDirective5</p>
+<pre><code class="language-sh">Simple:textDirectiveCode
+</code></pre>"
+`;
+
+exports[`directives remark plugin - server compiler default behavior for container directives: result 1`] = `
+"<admonition type="danger"><p>Take care of snowstorms...</p></admonition>
+<div><p>unused directive content</p></div>
+<p>:::NotAContainerDirective with a phrase after</p>
+<p>:::</p>
+<p>Phrase before :::NotAContainerDirective</p>
+<p>:::</p>"
+`;
+
+exports[`directives remark plugin - server compiler default behavior for leaf directives: result 1`] = `
+"<div></div>
+<p>Leaf directive in a phrase ::NotALeafDirective</p>
+<p>::NotALeafDirective with a phrase after</p>"
+`;
+
+exports[`directives remark plugin - server compiler default behavior for text directives: result 1`] = `
+"<p>Simple: textDirective1</p>
+<pre><code class="language-sh">Simple: textDirectiveCode
+</code></pre>
+<p>Simple:textDirective2</p>
+<p>Simple<div>label</div></p>
+<p>Simple<div></div></p>
+<p>Simple:textDirective5</p>
+<pre><code class="language-sh">Simple:textDirectiveCode
+</code></pre>"
+`;
diff --git a/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/index.test.ts b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/index.test.ts
new file mode 100644
index 0000000000000..77910e1e442c3
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/__tests__/index.test.ts
@@ -0,0 +1,111 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import path from 'path';
+import remark2rehype from 'remark-rehype';
+import stringify from 'rehype-stringify';
+import vfile from 'to-vfile';
+import plugin from '../index';
+import admonition from '../../admonitions';
+import type {WebpackCompilerName} from '@docusaurus/utils';
+
+const processFixture = async (
+  name: string,
+  {compilerName}: {compilerName: WebpackCompilerName},
+) => {
+  const {remark} = await import('remark');
+  const {default: directives} = await import('remark-directive');
+
+  const filePath = path.join(__dirname, '__fixtures__', `${name}.md`);
+  const file = await vfile.read(filePath);
+  file.data.compilerName = compilerName;
+
+  const result = await remark()
+    .use(directives)
+    .use(admonition)
+    .use(plugin)
+    .use(remark2rehype)
+    .use(stringify)
+    .process(file);
+
+  return result.value;
+};
+
+describe('directives remark plugin - client compiler', () => {
+  const consoleMock = jest.spyOn(console, 'warn').mockImplementation(() => {});
+  beforeEach(() => jest.clearAllMocks());
+
+  const options = {compilerName: 'client'} as const;
+
+  it('default behavior for container directives', async () => {
+    const result = await processFixture('containerDirectives', options);
+    expect(result).toMatchSnapshot('result');
+    expect(consoleMock).toHaveBeenCalledTimes(1);
+    expect(consoleMock.mock.calls).toMatchSnapshot('console');
+  });
+
+  it('default behavior for leaf directives', async () => {
+    const result = await processFixture('leafDirectives', options);
+    expect(result).toMatchSnapshot('result');
+    expect(consoleMock).toHaveBeenCalledTimes(1);
+    expect(consoleMock.mock.calls).toMatchSnapshot('console');
+  });
+
+  it('default behavior for text directives', async () => {
+    const result = await processFixture('textDirectives', options);
+    expect(result).toMatchSnapshot('result');
+    expect(consoleMock).toHaveBeenCalledTimes(1);
+    expect(consoleMock.mock.calls).toMatchSnapshot('console');
+  });
+});
+
+describe('directives remark plugin - server compiler', () => {
+  const consoleMock = jest.spyOn(console, 'warn').mockImplementation(() => {});
+  beforeEach(() => jest.clearAllMocks());
+
+  const options = {compilerName: 'server'} as const;
+
+  it('default behavior for container directives', async () => {
+    const result = await processFixture('containerDirectives', options);
+    expect(result).toMatchSnapshot('result');
+    expect(consoleMock).toHaveBeenCalledTimes(0);
+  });
+
+  it('default behavior for leaf directives', async () => {
+    const result = await processFixture('leafDirectives', options);
+    expect(result).toMatchSnapshot('result');
+    expect(consoleMock).toHaveBeenCalledTimes(0);
+  });
+
+  it('default behavior for text directives', async () => {
+    const result = await processFixture('textDirectives', options);
+    expect(result).toMatchSnapshot('result');
+    expect(consoleMock).toHaveBeenCalledTimes(0);
+  });
+});
+
+describe('directives remark plugin - client result === server result', () => {
+  // It is important that client/server outputs are exactly the same
+  // otherwise React hydration mismatches can occur
+  async function testSameResult(name: string) {
+    const resultClient = await processFixture(name, {compilerName: 'client'});
+    const resultServer = await processFixture(name, {compilerName: 'server'});
+    expect(resultClient).toEqual(resultServer);
+  }
+
+  it('for containerDirectives', async () => {
+    await testSameResult('containerDirectives');
+  });
+
+  it('for leafDirectives', async () => {
+    await testSameResult('leafDirectives');
+  });
+
+  it('for textDirectives', async () => {
+    await testSameResult('textDirectives');
+  });
+});
diff --git a/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/index.ts b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/index.ts
new file mode 100644
index 0000000000000..99d0a1dfa6e70
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/remark/unusedDirectives/index.ts
@@ -0,0 +1,162 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+import path from 'path';
+import process from 'process';
+import visit from 'unist-util-visit';
+import logger from '@docusaurus/logger';
+import {posixPath} from '@docusaurus/utils';
+import {transformNode} from '../utils';
+
+// @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
+import type {Transformer, Processor, Parent} from 'unified';
+import type {
+  Directive,
+  TextDirective,
+  // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
+} from 'mdast-util-directive';
+
+// TODO as of April 2023, no way to import/re-export this ESM type easily :/
+// This might change soon, likely after TS 5.2
+// See https://github.com/microsoft/TypeScript/issues/49721#issuecomment-1517839391
+// import type {Plugin} from 'unified';
+type Plugin = any; // TODO fix this asap
+
+type DirectiveType = Directive['type'];
+
+const directiveTypes: DirectiveType[] = [
+  'containerDirective',
+  'leafDirective',
+  'textDirective',
+];
+
+const directivePrefixMap: {[key in DirectiveType]: string} = {
+  textDirective: ':',
+  leafDirective: '::',
+  containerDirective: ':::',
+};
+
+function formatDirectiveName(directive: Directive) {
+  const prefix = directivePrefixMap[directive.type];
+  if (!prefix) {
+    throw new Error(
+      `unexpected, no prefix found for directive of type ${directive.type}`,
+    );
+  }
+  // To simplify we don't display the eventual label/props of directives
+  return `${prefix}${directive.name}`;
+}
+
+function formatDirectivePosition(directive: Directive): string | undefined {
+  return directive.position?.start
+    ? logger.interpolate`number=${directive.position.start.line}:number=${directive.position.start.column}`
+    : undefined;
+}
+
+function formatUnusedDirectiveMessage(directive: Directive) {
+  const name = formatDirectiveName(directive);
+  const position = formatDirectivePosition(directive);
+
+  return `- ${name} ${position ? `(${position})` : ''}`;
+}
+
+function formatUnusedDirectivesMessage({
+  directives,
+  filePath,
+}: {
+  directives: Directive[];
+  filePath: string;
+}): string {
+  const supportUrl = 'https://github.com/facebook/docusaurus/pull/9394';
+  const customPath = posixPath(path.relative(process.cwd(), filePath));
+  const warningTitle = logger.interpolate`Docusaurus found ${directives.length} unused Markdown directives in file path=${customPath}`;
+  const customSupportUrl = logger.interpolate`url=${supportUrl}`;
+  const warningMessages = directives
+    .map(formatUnusedDirectiveMessage)
+    .join('\n');
+
+  return `${warningTitle}
+${warningMessages}
+Your content might render in an unexpected way. Visit ${customSupportUrl} to find out why and how to fix it.`;
+}
+
+function logUnusedDirectivesWarning({
+  directives,
+  filePath,
+}: {
+  directives: Directive[];
+  filePath: string;
+}) {
+  if (directives.length > 0) {
+    const message = formatUnusedDirectivesMessage({
+      directives,
+      filePath,
+    });
+    logger.warn(message);
+  }
+}
+
+function isTextDirective(directive: Directive): directive is TextDirective {
+  return directive.type === 'textDirective';
+}
+
+// A simple text directive is one without any label/props
+function isSimpleTextDirective(
+  directive: Directive,
+): directive is TextDirective {
+  if (isTextDirective(directive)) {
+    // Attributes in MDAST = Directive props
+    const hasAttributes =
+      directive.attributes && Object.keys(directive.attributes).length > 0;
+    // Children in MDAST = Directive label
+    const hasChildren = directive.children.length > 0;
+    return !hasAttributes && !hasChildren;
+  }
+  return false;
+}
+
+function transformSimpleTextDirectiveToString(textDirective: Directive) {
+  transformNode(textDirective, {
+    type: 'text',
+    value: `:${textDirective.name}`, // We ignore label/props on purpose here
+  });
+}
+
+function isUnusedDirective(directive: Directive) {
+  // If directive data is set (notably hName/hProperties set by admonitions)
+  // this usually means the directive has been handled by another plugin
+  return !directive.data;
+}
+
+const plugin: Plugin = function plugin(this: Processor): Transformer {
+  return (tree, file) => {
+    const unusedDirectives: Directive[] = [];
+
+    visit<Parent>(tree, directiveTypes, (directive: Directive) => {
+      // If directive data is set (notably hName/hProperties set by admonitions)
+      // this usually means the directive has been handled by another plugin
+      if (isUnusedDirective(directive)) {
+        if (isSimpleTextDirective(directive)) {
+          transformSimpleTextDirectiveToString(directive);
+        } else {
+          unusedDirectives.push(directive);
+        }
+      }
+    });
+
+    // We only enable these warnings for the client compiler
+    // This avoids emitting duplicate warnings in prod mode
+    // Note: the client compiler is used in both dev/prod modes
+    if (file.data.compilerName === 'client') {
+      logUnusedDirectivesWarning({
+        directives: unusedDirectives,
+        filePath: file.path,
+      });
+    }
+  };
+};
+
+export default plugin;
diff --git a/packages/docusaurus-mdx-loader/src/remark/utils/index.ts b/packages/docusaurus-mdx-loader/src/remark/utils/index.ts
index 46e9591762397..3b29be807e2db 100644
--- a/packages/docusaurus-mdx-loader/src/remark/utils/index.ts
+++ b/packages/docusaurus-mdx-loader/src/remark/utils/index.ts
@@ -6,7 +6,7 @@
  */
 
 import escapeHtml from 'escape-html';
-import type {Parent} from 'unist';
+import type {Parent, Node} from 'unist';
 import type {PhrasingContent, Heading} from 'mdast';
 import type {
   MdxJsxAttribute,
@@ -15,6 +15,27 @@ import type {
   // @ts-expect-error: TODO see https://github.com/microsoft/TypeScript/issues/49721
 } from 'mdast-util-mdx';
 
+/**
+ * Util to transform one node type to another node type
+ * The input node is mutated in place
+ * @param node the node to mutate
+ * @param newNode what the original node should become become
+ */
+export function transformNode<NewNode extends Node>(
+  node: Node,
+  newNode: NewNode,
+): NewNode {
+  Object.keys(node).forEach((key) => {
+    // @ts-expect-error: unsafe but ok
+    delete node[key];
+  });
+  Object.keys(newNode).forEach((key) => {
+    // @ts-expect-error: unsafe but ok
+    node[key] = newNode[key];
+  });
+  return node as NewNode;
+}
+
 export function stringifyContent(
   node: Parent,
   toString: (param: unknown) => string, // TODO weird but works
diff --git a/packages/docusaurus-mdx-loader/src/vfile-datamap.d.mts b/packages/docusaurus-mdx-loader/src/vfile-datamap.d.mts
new file mode 100644
index 0000000000000..2538305411c82
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/src/vfile-datamap.d.mts
@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import type {WebpackCompilerName} from '@docusaurus/utils';
+
+declare module 'vfile' {
+  /*
+  This map registers the type of the data key of a VFile (TypeScript type).
+  This type can be augmented to register custom data types.
+  See https://github.com/vfile/vfile#datamap
+   */
+  interface DataMap {
+    frontMatter: {[key: string]: unknown};
+    compilerName: WebpackCompilerName;
+    contentTitle?: string;
+  }
+}
diff --git a/packages/docusaurus-utils/src/index.ts b/packages/docusaurus-utils/src/index.ts
index d5cabc65301aa..5bb77a0c054f0 100644
--- a/packages/docusaurus-utils/src/index.ts
+++ b/packages/docusaurus-utils/src/index.ts
@@ -98,7 +98,11 @@ export {
   createMatcher,
   createAbsoluteFilePathMatcher,
 } from './globUtils';
-export {getFileLoaderUtils} from './webpackUtils';
+export {
+  getFileLoaderUtils,
+  getWebpackLoaderCompilerName,
+  type WebpackCompilerName,
+} from './webpackUtils';
 export {escapeShellArg} from './shellUtils';
 export {loadFreshModule} from './moduleUtils';
 export {
diff --git a/packages/docusaurus-utils/src/webpackUtils.ts b/packages/docusaurus-utils/src/webpackUtils.ts
index c1195d5764b37..411b5a0fee22b 100644
--- a/packages/docusaurus-utils/src/webpackUtils.ts
+++ b/packages/docusaurus-utils/src/webpackUtils.ts
@@ -11,7 +11,25 @@ import {
   WEBPACK_URL_LOADER_LIMIT,
   OUTPUT_STATIC_ASSETS_DIR_NAME,
 } from './constants';
-import type {RuleSetRule} from 'webpack';
+import type {RuleSetRule, LoaderContext} from 'webpack';
+
+export type WebpackCompilerName = 'server' | 'client';
+
+export function getWebpackLoaderCompilerName(
+  context: LoaderContext<unknown>,
+): WebpackCompilerName {
+  // eslint-disable-next-line no-underscore-dangle
+  const compilerName = context._compiler?.name;
+  switch (compilerName) {
+    case 'server':
+    case 'client':
+      return compilerName;
+    default:
+      throw new Error(
+        `Cannot get valid Docusaurus webpack compiler name. Found compilerName=${compilerName}`,
+      );
+  }
+}
 
 type AssetFolder = 'images' | 'files' | 'fonts' | 'medias';
 
diff --git a/project-words.txt b/project-words.txt
index 1f9e8bada8efd..fdc8d43a57fc6 100644
--- a/project-words.txt
+++ b/project-words.txt
@@ -62,6 +62,7 @@ customizability
 dabit
 daishi
 datagit
+datamap
 datas
 dbaeumer
 décembre