diff --git a/package.json b/package.json
index 20eab0a7..20a59cad 100644
--- a/package.json
+++ b/package.json
@@ -132,8 +132,10 @@
     "remark": "^15.0.0",
     "remark-cli": "^12.0.0",
     "remark-comment-config": "^8.0.0",
+    "remark-directive": "^3.0.0",
     "remark-gfm": "^4.0.0",
     "remark-github": "^12.0.0",
+    "remark-math": "^6.0.0",
     "remark-mdx": "^3.0.0",
     "remark-toc": "^9.0.0",
     "remark-validate-links": "^13.0.0",
diff --git a/packages/remark-lint-definition-case/index.js b/packages/remark-lint-definition-case/index.js
index 5fae127a..bec81d64 100644
--- a/packages/remark-lint-definition-case/index.js
+++ b/packages/remark-lint-definition-case/index.js
@@ -51,6 +51,16 @@
  *   {"name": "not-ok.md", "label": "output"}
  *
  *   1:1-1:47: Do not use uppercase characters in definition labels
+ *
+ * @example
+ *   {"gfm": true, "label": "input", "name": "gfm.md"}
+ *
+ *   [^X]: Footnote definitions (from GFM) are checked too.
+ *
+ * @example
+ *   {"gfm": true, "label": "output", "name": "gfm.md"}
+ *
+ *   1:1-1:55: Do not use uppercase characters in definition labels
  */
 
 /**
diff --git a/packages/remark-lint-definition-case/readme.md b/packages/remark-lint-definition-case/readme.md
index 9ce5d1f9..4414f6c2 100644
--- a/packages/remark-lint-definition-case/readme.md
+++ b/packages/remark-lint-definition-case/readme.md
@@ -167,6 +167,23 @@ No messages.
 1:1-1:47: Do not use uppercase characters in definition labels
 ```
 
+##### `gfm.md`
+
+###### In
+
+> 👉 **Note**: this example uses
+> GFM ([`remark-gfm`][github-remark-gfm]).
+
+```markdown
+[^X]: Footnote definitions (from GFM) are checked too.
+```
+
+###### Out
+
+```text
+1:1-1:55: Do not use uppercase characters in definition labels
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -236,6 +253,8 @@ abide by its terms.
 
 [github-gist-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
 
+[github-remark-gfm]: https://github.com/remarkjs/remark-gfm
+
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
diff --git a/packages/remark-lint-definition-spacing/index.js b/packages/remark-lint-definition-spacing/index.js
index 6e23bf2a..610ac1d2 100644
--- a/packages/remark-lint-definition-spacing/index.js
+++ b/packages/remark-lint-definition-spacing/index.js
@@ -6,6 +6,9 @@
  *
  * This package checks the whitepsace in definition labels.
  *
+ * GFM footnotes are not affected by this rule as footnote labels cannot
+ * contain whitespace.
+ *
  * ## When should I use this?
  *
  * You can use this package to check that definition labels are consistent.
@@ -79,7 +82,7 @@ const remarkLintDefinitionSpacing = lintRule(
     const value = String(file)
 
     visit(tree, function (node) {
-      if (node.type === 'definition' || node.type === 'footnoteDefinition') {
+      if (node.type === 'definition') {
         const end = pointEnd(node)
         const start = pointStart(node)
 
diff --git a/packages/remark-lint-definition-spacing/readme.md b/packages/remark-lint-definition-spacing/readme.md
index 182efd4c..3d3482f4 100644
--- a/packages/remark-lint-definition-spacing/readme.md
+++ b/packages/remark-lint-definition-spacing/readme.md
@@ -32,6 +32,9 @@ a definition label.
 
 This package checks the whitepsace in definition labels.
 
+GFM footnotes are not affected by this rule as footnote labels cannot
+contain whitespace.
+
 ## When should I use this?
 
 You can use this package to check that definition labels are consistent.
diff --git a/packages/remark-lint-file-extension/index.js b/packages/remark-lint-file-extension/index.js
index 99f60f17..97426321 100644
--- a/packages/remark-lint-file-extension/index.js
+++ b/packages/remark-lint-file-extension/index.js
@@ -20,8 +20,8 @@
  *
  * ###### Parameters
  *
- * * `options` (`string`, default: `'md'`)
- *   — preferred file extension
+ * * `options` (`Array<string>` or `string`, default: `['mdx', 'md']`)
+ *   — allowed file extension(s)
  *
  * ###### Returns
  *
@@ -50,7 +50,7 @@
  * @example
  *   {"name": "readme.mkd", "label": "output", "positionless": true}
  *
- *   1:1: Incorrect extension: use `md`
+ *   1:1: Incorrect extension: use `mdx` or `md`
  *
  * @example
  *   {"name": "readme.mkd", "config": "mkd"}
@@ -61,6 +61,12 @@
  */
 
 import {lintRule} from 'unified-lint-rule'
+import {quotation} from 'quotation'
+
+/** @type {ReadonlyArray<string>} */
+const defaultExtensions = ['mdx', 'md']
+
+const listFormat = new Intl.ListFormat('en', {type: 'disjunction'})
 
 const remarkLintFileExtension = lintRule(
   {
@@ -70,17 +76,22 @@ const remarkLintFileExtension = lintRule(
   /**
    * @param {Root} _
    *   Tree.
-   * @param {string | null | undefined} [options='md']
+   * @param {ReadonlyArray<string> | string | null | undefined} [options='md']
    *   Configuration (default: `'md'`).
    * @returns {undefined}
    *   Nothing.
    */
   function (_, file, options) {
-    const option = options || 'md'
-    const ext = file.extname
+    const extensions =
+      typeof options === 'string' ? [options] : options || defaultExtensions
+    const extname = file.extname
+    const extension = extname ? extname.slice(1) : undefined
 
-    if (ext && ext.slice(1) !== option) {
-      file.message('Incorrect extension: use `' + option + '`')
+    if (extension && !extensions.includes(extension)) {
+      file.message(
+        'Incorrect extension: use ' +
+          listFormat.format(quotation(extensions, '`'))
+      )
     }
   }
 )
diff --git a/packages/remark-lint-file-extension/package.json b/packages/remark-lint-file-extension/package.json
index 8d77c699..5489d172 100644
--- a/packages/remark-lint-file-extension/package.json
+++ b/packages/remark-lint-file-extension/package.json
@@ -33,6 +33,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "quotation": "^2.0.0",
     "unified-lint-rule": "^2.0.0"
   },
   "scripts": {},
diff --git a/packages/remark-lint-file-extension/readme.md b/packages/remark-lint-file-extension/readme.md
index b3d20e2b..b6035b84 100644
--- a/packages/remark-lint-file-extension/readme.md
+++ b/packages/remark-lint-file-extension/readme.md
@@ -129,8 +129,8 @@ Warn for unexpected extensions.
 
 ###### Parameters
 
-* `options` (`string`, default: `'md'`)
-  — preferred file extension
+* `options` (`Array<string>` or `string`, default: `['mdx', 'md']`)
+  — allowed file extension(s)
 
 ###### Returns
 
@@ -162,7 +162,7 @@ No messages.
 ###### Out
 
 ```text
-1:1: Incorrect extension: use `md`
+1:1: Incorrect extension: use `mdx` or `md`
 ```
 
 ##### `readme.mkd`
diff --git a/packages/remark-lint-final-definition/index.js b/packages/remark-lint-final-definition/index.js
index c4812b2d..252c140f 100644
--- a/packages/remark-lint-final-definition/index.js
+++ b/packages/remark-lint-final-definition/index.js
@@ -119,8 +119,6 @@ const remarkLintFinalDefinition = lintRule(
         definitions.push(node)
       } else if (
         node.type === 'root' ||
-        node.type === 'blockquote' ||
-        node.type === 'listItem' ||
         // Ignore HTML comments.
         (node.type === 'html' && /^[\t ]*<!--/.test(node.value)) ||
         // Ignore MDX comments.
diff --git a/packages/remark-lint-first-heading-level/index.js b/packages/remark-lint-first-heading-level/index.js
index 86835d3a..c31098da 100644
--- a/packages/remark-lint-first-heading-level/index.js
+++ b/packages/remark-lint-first-heading-level/index.js
@@ -52,7 +52,8 @@
  * In some cases a different rank makes more sense,
  * such as when building a blog and generating the primary heading from
  * frontmatter metadata,
- * in which case a value of `2` can be defined here.
+ * in which case a value of `2` can be defined here or the rule can be turned
+ * off.
  *
  * [api-depth]: #depth
  * [api-options]: #options
@@ -145,9 +146,9 @@
  *   1:1-1:14: First heading level should be `2`
  *
  * @example
- *   {"name": "ok.mdx", "mdx": true}
+ *   {"mdx": true, "name": "ok.mdx"}
  *
- *   In <b>MDX</b>, JSX is supported.
+ *   In MDX, <b>JSX</b> is supported.
  *
  *   <h1>First heading</h1>
  */
@@ -172,7 +173,7 @@ import {position} from 'unist-util-position'
 import {EXIT, visit} from 'unist-util-visit'
 
 const htmlRe = /<h([1-6])/
-const jsxNameRe = /h([1-6])/
+const jsxNameRe = /^h([1-6])$/
 
 const remarkLintFirstHeadingLevel = lintRule(
   {
@@ -191,36 +192,31 @@ const remarkLintFirstHeadingLevel = lintRule(
     const option = options || 1
 
     visit(tree, function (node) {
-      const place = position(node)
+      /** @type {Depth | undefined} */
+      let rank
 
-      if (place) {
-        /** @type {Depth | undefined} */
-        let rank
-
-        if (node.type === 'heading') {
-          rank = node.depth
-        } else if (node.type === 'html') {
-          const results = node.value.match(htmlRe)
-          rank = results ? /** @type {Depth} */ (Number(results[1])) : undefined
-        } else if (
-          (node.type === 'mdxJsxFlowElement' ||
-            node.type === 'mdxJsxTextElement') &&
-          node.name
-        ) {
-          const results = node.name.match(jsxNameRe)
-          rank = results ? /** @type {Depth} */ (Number(results[1])) : undefined
-        }
+      if (node.type === 'heading') {
+        rank = node.depth
+      } else if (node.type === 'html') {
+        const results = node.value.match(htmlRe)
+        rank = results ? /** @type {Depth} */ (Number(results[1])) : undefined
+      } else if (
+        (node.type === 'mdxJsxFlowElement' ||
+          node.type === 'mdxJsxTextElement') &&
+        node.name
+      ) {
+        const results = node.name.match(jsxNameRe)
+        rank = results ? /** @type {Depth} */ (Number(results[1])) : undefined
+      }
 
-        if (rank) {
-          if (rank !== option) {
-            file.message(
-              'First heading level should be `' + option + '`',
-              place
-            )
-          }
+      if (rank) {
+        const place = position(node)
 
-          return EXIT
+        if (place && rank !== option) {
+          file.message('First heading level should be `' + option + '`', place)
         }
+
+        return EXIT
       }
     })
   }
diff --git a/packages/remark-lint-first-heading-level/readme.md b/packages/remark-lint-first-heading-level/readme.md
index a0a4c0c1..53c5f34e 100644
--- a/packages/remark-lint-first-heading-level/readme.md
+++ b/packages/remark-lint-first-heading-level/readme.md
@@ -161,7 +161,8 @@ rank `1`.
 In some cases a different rank makes more sense,
 such as when building a blog and generating the primary heading from
 frontmatter metadata,
-in which case a value of `2` can be defined here.
+in which case a value of `2` can be defined here or the rule can be turned
+off.
 
 ## Examples
 
@@ -313,7 +314,7 @@ Paragraph.
 > MDX ([`remark-mdx`][github-remark-mdx]).
 
 ```mdx
-In <b>MDX</b>, JSX is supported.
+In MDX, <b>JSX</b> is supported.
 
 <h1>First heading</h1>
 ```
diff --git a/packages/remark-lint-heading-increment/index.js b/packages/remark-lint-heading-increment/index.js
index b1f9609c..754b24a5 100644
--- a/packages/remark-lint-heading-increment/index.js
+++ b/packages/remark-lint-heading-increment/index.js
@@ -62,6 +62,20 @@
  *   {"name": "not-ok.md", "label": "output"}
  *
  *   3:1-3:10: Heading levels should increment by one level at a time
+ *
+ * @example
+ *   {"name": "html.md"}
+ *
+ *   In markdown, <b>HTML</b> is supported.
+ *
+ *   <h1>First heading</h1>
+ *
+ * @example
+ *   {"name": "ok.mdx", "mdx": true}
+ *
+ *   In MDX, <b>JSX</b> is supported.
+ *
+ *   <h1>First heading</h1>
  */
 
 /**
@@ -69,10 +83,15 @@
  * @typedef {import('mdast').Root} Root
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {lintRule} from 'unified-lint-rule'
 import {position} from 'unist-util-position'
 import {visit} from 'unist-util-visit'
 
+const htmlRe = /<h([1-6])/
+const jsxNameRe = /^h([1-6])$/
+
 const remarkLintHeadingIncrement = lintRule(
   {
     origin: 'remark-lint:heading-increment',
@@ -88,18 +107,41 @@ const remarkLintHeadingIncrement = lintRule(
     /** @type {Heading['depth'] | undefined} */
     let previous
 
-    visit(tree, 'heading', function (node) {
+    visit(tree, function (node) {
       const place = position(node)
 
       if (place) {
-        if (previous && node.depth > previous + 1) {
-          file.message(
-            'Heading levels should increment by one level at a time',
-            place
-          )
+        /** @type {Heading['depth'] | undefined} */
+        let rank
+
+        if (node.type === 'heading') {
+          rank = node.depth
+        } else if (node.type === 'html') {
+          const results = node.value.match(htmlRe)
+          rank = results
+            ? /** @type {Heading['depth']} */ (Number(results[1]))
+            : undefined
+        } else if (
+          (node.type === 'mdxJsxFlowElement' ||
+            node.type === 'mdxJsxTextElement') &&
+          node.name
+        ) {
+          const results = node.name.match(jsxNameRe)
+          rank = results
+            ? /** @type {Heading['depth']} */ (Number(results[1]))
+            : undefined
         }
 
-        previous = node.depth
+        if (rank) {
+          if (previous && rank > previous + 1) {
+            file.message(
+              'Heading levels should increment by one level at a time',
+              place
+            )
+          }
+
+          previous = rank
+        }
       }
     })
   }
diff --git a/packages/remark-lint-heading-increment/package.json b/packages/remark-lint-heading-increment/package.json
index fd6a50f2..ba17bb0e 100644
--- a/packages/remark-lint-heading-increment/package.json
+++ b/packages/remark-lint-heading-increment/package.json
@@ -33,6 +33,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
     "unist-util-visit": "^5.0.0"
diff --git a/packages/remark-lint-heading-increment/readme.md b/packages/remark-lint-heading-increment/readme.md
index fedb5ece..55551d02 100644
--- a/packages/remark-lint-heading-increment/readme.md
+++ b/packages/remark-lint-heading-increment/readme.md
@@ -178,6 +178,37 @@ No messages.
 3:1-3:10: Heading levels should increment by one level at a time
 ```
 
+##### `html.md`
+
+###### In
+
+```markdown
+In markdown, <b>HTML</b> is supported.
+
+<h1>First heading</h1>
+```
+
+###### Out
+
+No messages.
+
+##### `ok.mdx`
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+In MDX, <b>JSX</b> is supported.
+
+<h1>First heading</h1>
+```
+
+###### Out
+
+No messages.
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -249,6 +280,8 @@ abide by its terms.
 
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
 
 [npm-install]: https://docs.npmjs.com/cli/install
diff --git a/packages/remark-lint-maximum-heading-length/index.js b/packages/remark-lint-maximum-heading-length/index.js
index 7952301e..f4bfa142 100644
--- a/packages/remark-lint-maximum-heading-length/index.js
+++ b/packages/remark-lint-maximum-heading-length/index.js
@@ -56,17 +56,30 @@
  *   {"name": "not-ok.md", "config": 40, "label": "output"}
  *
  *   1:1-1:52: Use headings shorter than `40`
+ *
+ * @example
+ *   {"config": 30, "label": "input", "mdx": true, "name": "ok.mdx"}
+ *
+ *   <h1>In MDX, headings are checked too</h1>
+ * @example
+ *   {"config": 30, "label": "output", "mdx": true, "name": "ok.mdx"}
+ *
+ *   1:1-1:42: Use headings shorter than `30`
  */
 
 /**
  * @typedef {import('mdast').Root} Root
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {toString} from 'mdast-util-to-string'
 import {lintRule} from 'unified-lint-rule'
 import {position} from 'unist-util-position'
 import {visit} from 'unist-util-visit'
 
+const jsxNameRe = /^h([1-6])$/
+
 const remarkLintMaximumHeadingLength = lintRule(
   {
     origin: 'remark-lint:maximum-heading-length',
@@ -83,11 +96,23 @@ const remarkLintMaximumHeadingLength = lintRule(
   function (tree, file, options) {
     const option = options || 60
 
-    visit(tree, 'heading', function (node) {
-      const place = position(node)
+    // Note: HTML headings cannot properly be checked,
+    // because for markdown, blocks are one single raw string.
+
+    visit(tree, function (node) {
+      if (
+        node.type === 'heading' ||
+        ((node.type === 'mdxJsxFlowElement' ||
+          node.type === 'mdxJsxTextElement') &&
+          node.name &&
+          jsxNameRe.test(node.name))
+      ) {
+        const place = position(node)
+        const codePoints = Array.from(toString(node, {includeHtml: false}))
 
-      if (place && toString(node).length > option) {
-        file.message('Use headings shorter than `' + option + '`', place)
+        if (place && codePoints.length > option) {
+          file.message('Use headings shorter than `' + option + '`', place)
+        }
       }
     })
   }
diff --git a/packages/remark-lint-maximum-heading-length/package.json b/packages/remark-lint-maximum-heading-length/package.json
index bb539b80..0a2b8c7c 100644
--- a/packages/remark-lint-maximum-heading-length/package.json
+++ b/packages/remark-lint-maximum-heading-length/package.json
@@ -32,6 +32,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "mdast-util-to-string": "^4.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
diff --git a/packages/remark-lint-maximum-heading-length/readme.md b/packages/remark-lint-maximum-heading-length/readme.md
index 24677d21..1ecfc84a 100644
--- a/packages/remark-lint-maximum-heading-length/readme.md
+++ b/packages/remark-lint-maximum-heading-length/readme.md
@@ -174,6 +174,25 @@ When configured with `40`.
 1:1-1:52: Use headings shorter than `40`
 ```
 
+##### `ok.mdx`
+
+When configured with `30`.
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+<h1>In MDX, headings are checked too</h1>
+```
+
+###### Out
+
+```text
+1:1-1:42: Use headings shorter than `30`
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -245,6 +264,8 @@ abide by its terms.
 
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
 
 [npm-install]: https://docs.npmjs.com/cli/install
diff --git a/packages/remark-lint-maximum-line-length/index.js b/packages/remark-lint-maximum-line-length/index.js
index 18e14fb6..1c2ba7bd 100644
--- a/packages/remark-lint-maximum-line-length/index.js
+++ b/packages/remark-lint-maximum-line-length/index.js
@@ -119,12 +119,12 @@
  *   4:12: Line must be at most 10 characters
  */
 
-/// <reference types="mdast-util-mdx" />
-
 /**
  * @typedef {import('mdast').Root} Root
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {lintRule} from 'unified-lint-rule'
 import {pointEnd, pointStart} from 'unist-util-position'
 import {visit} from 'unist-util-visit'
@@ -147,6 +147,7 @@ const remarkLintMaximumLineLength = lintRule(
     const lines = value.split(/\r?\n/)
     const option = options || 80
 
+    // Allow nodes that cannot be wrapped.
     visit(tree, function (node) {
       if (
         node.type === 'code' ||
@@ -169,11 +170,8 @@ const remarkLintMaximumLineLength = lintRule(
       }
     })
 
-    // Finally, allow some inline spans, but only if they occur at or after
-    // the wrap.
-    // However, when they do, and there’s whitespace after it, they are not
-    // allowed.
-    visit(tree, function (node, pos, parent) {
+    // Allow text spans to cross the border.
+    visit(tree, function (node, index, parent) {
       const final = pointEnd(node)
       const initial = pointStart(node)
 
@@ -184,14 +182,14 @@ const remarkLintMaximumLineLength = lintRule(
         initial &&
         final &&
         parent &&
-        typeof pos === 'number'
+        typeof index === 'number'
       ) {
         // Not allowing when starting after the border, or ending before it.
         if (initial.column > option || final.column < option) {
           return
         }
 
-        const next = parent.children[pos + 1]
+        const next = parent.children[index + 1]
         const nextStart = pointStart(next)
 
         // Not allowing when there’s whitespace after the link.
@@ -208,7 +206,7 @@ const remarkLintMaximumLineLength = lintRule(
       }
     })
 
-    // Iterate over every line, and warn for violating lines.
+    // Iterate over every line and warn for violating lines.
     let index = -1
 
     while (++index < lines.length) {
diff --git a/packages/remark-lint-no-duplicate-definitions/index.js b/packages/remark-lint-no-duplicate-definitions/index.js
index e03605cd..8966e72e 100644
--- a/packages/remark-lint-no-duplicate-definitions/index.js
+++ b/packages/remark-lint-no-duplicate-definitions/index.js
@@ -50,6 +50,19 @@
  *   {"name": "not-ok.md", "label": "output"}
  *
  *   2:1-2:11: Do not use definitions with the same identifier (1:1)
+ *
+ * @example
+ *   {"gfm": true, "label": "input", "name": "gfm.md"}
+ *
+ *   GFM footnote definitions are checked too[^a].
+ *
+ *   [^a]: alpha
+ *   [^a]: bravo
+ *
+ * @example
+ *   {"gfm": true, "label": "output", "name": "gfm.md"}
+ *
+ *   4:1-4:12: Do not use footnote definitions with the same identifier (3:1)
  */
 
 /**
@@ -61,6 +74,9 @@ import {pointStart, position} from 'unist-util-position'
 import {stringifyPosition} from 'unist-util-stringify-position'
 import {visit} from 'unist-util-visit'
 
+/** @type {ReadonlyArray<never>} */
+const empty = []
+
 const remarkLintNoDuplicateDefinitions = lintRule(
   {
     origin: 'remark-lint:no-duplicate-definitions',
@@ -74,23 +90,28 @@ const remarkLintNoDuplicateDefinitions = lintRule(
    */
   function (tree, file) {
     /** @type {Map<string, string>} */
-    const map = new Map()
+    const definitions = new Map()
+    /** @type {Map<string, string>} */
+    const footnoteDefinitions = new Map()
 
     visit(tree, function (node) {
       const place = position(node)
       const start = pointStart(node)
+      const [map, identifier] =
+        node.type === 'definition'
+          ? [definitions, node.identifier]
+          : node.type === 'footnoteDefinition'
+            ? [footnoteDefinitions, node.identifier]
+            : empty
 
-      if (
-        (node.type === 'definition' || node.type === 'footnoteDefinition') &&
-        place &&
-        start
-      ) {
-        const identifier = node.identifier
+      if (map && identifier && place && start) {
         const duplicate = map.get(identifier)
 
         if (duplicate) {
           file.message(
-            'Do not use definitions with the same identifier (' +
+            'Do not use' +
+              (node.type === 'footnoteDefinition' ? ' footnote' : '') +
+              ' definitions with the same identifier (' +
               duplicate +
               ')',
             place
diff --git a/packages/remark-lint-no-duplicate-definitions/readme.md b/packages/remark-lint-no-duplicate-definitions/readme.md
index 7b34c803..2917bf68 100644
--- a/packages/remark-lint-no-duplicate-definitions/readme.md
+++ b/packages/remark-lint-no-duplicate-definitions/readme.md
@@ -166,6 +166,26 @@ No messages.
 2:1-2:11: Do not use definitions with the same identifier (1:1)
 ```
 
+##### `gfm.md`
+
+###### In
+
+> 👉 **Note**: this example uses
+> GFM ([`remark-gfm`][github-remark-gfm]).
+
+```markdown
+GFM footnote definitions are checked too[^a].
+
+[^a]: alpha
+[^a]: bravo
+```
+
+###### Out
+
+```text
+4:1-4:12: Do not use footnote definitions with the same identifier (3:1)
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -235,6 +255,8 @@ abide by its terms.
 
 [github-gist-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
 
+[github-remark-gfm]: https://github.com/remarkjs/remark-gfm
+
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
diff --git a/packages/remark-lint-no-duplicate-headings-in-section/index.js b/packages/remark-lint-no-duplicate-headings-in-section/index.js
index b63f555a..2c5a5f45 100644
--- a/packages/remark-lint-no-duplicate-headings-in-section/index.js
+++ b/packages/remark-lint-no-duplicate-headings-in-section/index.js
@@ -86,6 +86,19 @@
  *   {"name": "not-ok-tolerant-heading-increment.md", "label": "output"}
  *
  *   7:1-7:11: Do not use headings with similar content per section (3:1)
+ *
+ * @example
+ *   {"label": "input", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   MDX is supported <em>too</em>.
+ *
+ *   <h2>Alpha</h2>
+ *   <h2>Alpha</h2>
+ *
+ * @example
+ *   {"label": "output", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   4:1-4:15: Do not use headings with similar content per section (3:1)
  */
 
 /**
@@ -93,12 +106,16 @@
  * @typedef {import('mdast').Root} Root
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {toString} from 'mdast-util-to-string'
 import {lintRule} from 'unified-lint-rule'
 import {pointStart, position} from 'unist-util-position'
 import {stringifyPosition} from 'unist-util-stringify-position'
 import {visit} from 'unist-util-visit'
 
+const jsxNameRe = /^h([1-6])$/
+
 const remarkLintNoDuplicateHeadingsInSection = lintRule(
   {
     origin: 'remark-lint:no-duplicate-headings-in-section',
@@ -114,26 +131,44 @@ const remarkLintNoDuplicateHeadingsInSection = lintRule(
     /** @type {Array<Map<string, string>>} */
     const stack = []
 
-    visit(tree, 'heading', function (node) {
-      const value = toString(node).toUpperCase()
-      const index = node.depth - 1
-      const scope = stack[index] || (stack[index] = new Map())
-      const duplicate = scope.get(value)
-      const place = position(node)
-      const start = pointStart(node)
+    visit(tree, function (node) {
+      /** @type {Heading['depth'] | undefined} */
+      let rank
 
-      if (place && duplicate) {
-        file.message(
-          'Do not use headings with similar content per section (' +
-            duplicate +
-            ')',
-          place
-        )
+      if (node.type === 'heading') {
+        rank = node.depth
+      } else if (
+        (node.type === 'mdxJsxFlowElement' ||
+          node.type === 'mdxJsxTextElement') &&
+        node.name
+      ) {
+        const match = node.name.match(jsxNameRe)
+        rank = match
+          ? /** @type {Heading['depth']} */ (Number(match[1]))
+          : undefined
       }
 
-      scope.set(value, stringifyPosition(start))
-      // Drop things after it.
-      stack.length = node.depth
+      if (rank) {
+        const value = toString(node).toLowerCase()
+        const index = rank - 1
+        const scope = stack[index] || (stack[index] = new Map())
+        const duplicate = scope.get(value)
+        const place = position(node)
+        const start = pointStart(node)
+
+        if (place && duplicate) {
+          file.message(
+            'Do not use headings with similar content per section (' +
+              duplicate +
+              ')',
+            place
+          )
+        }
+
+        scope.set(value, stringifyPosition(start))
+        // Drop things after it.
+        stack.length = rank
+      }
     })
   }
 )
diff --git a/packages/remark-lint-no-duplicate-headings-in-section/package.json b/packages/remark-lint-no-duplicate-headings-in-section/package.json
index 15a9d5ef..9b8399c9 100644
--- a/packages/remark-lint-no-duplicate-headings-in-section/package.json
+++ b/packages/remark-lint-no-duplicate-headings-in-section/package.json
@@ -33,6 +33,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "mdast-util-to-string": "^4.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
diff --git a/packages/remark-lint-no-duplicate-headings-in-section/readme.md b/packages/remark-lint-no-duplicate-headings-in-section/readme.md
index 97ae6350..751697ab 100644
--- a/packages/remark-lint-no-duplicate-headings-in-section/readme.md
+++ b/packages/remark-lint-no-duplicate-headings-in-section/readme.md
@@ -202,6 +202,26 @@ No messages.
 7:1-7:11: Do not use headings with similar content per section (3:1)
 ```
 
+##### `mdx.mdx`
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+MDX is supported <em>too</em>.
+
+<h2>Alpha</h2>
+<h2>Alpha</h2>
+```
+
+###### Out
+
+```text
+4:1-4:15: Do not use headings with similar content per section (3:1)
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -273,6 +293,8 @@ abide by its terms.
 
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
 
 [npm-install]: https://docs.npmjs.com/cli/install
diff --git a/packages/remark-lint-no-duplicate-headings/index.js b/packages/remark-lint-no-duplicate-headings/index.js
index 05bcf101..f54e2c63 100644
--- a/packages/remark-lint-no-duplicate-headings/index.js
+++ b/packages/remark-lint-no-duplicate-headings/index.js
@@ -50,7 +50,7 @@
  *   ## Bar
  *
  * @example
- *   {"name": "not-ok.md", "label": "input"}
+ *   {"label": "input", "name": "not-ok.md"}
  *
  *   # Foo
  *
@@ -59,22 +59,39 @@
  *   ## [Foo](http://foo.com/bar)
  *
  * @example
- *   {"name": "not-ok.md", "label": "output"}
+ *   {"label": "output", "name": "not-ok.md"}
  *
  *   3:1-3:7: Do not use headings with similar content (1:1)
  *   5:1-5:29: Do not use headings with similar content (3:1)
+ *
+ * @example
+ *   {"label": "input", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   MDX is supported too.
+ *
+ *   <h1>Alpha</h1>
+ *   <h2>Alpha</h2>
+ *
+ * @example
+ *   {"label": "output", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   4:1-4:15: Do not use headings with similar content (3:1)
  */
 
 /**
  * @typedef {import('mdast').Root} Root
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {toString} from 'mdast-util-to-string'
 import {lintRule} from 'unified-lint-rule'
 import {pointStart, position} from 'unist-util-position'
 import {stringifyPosition} from 'unist-util-stringify-position'
 import {visit} from 'unist-util-visit'
 
+const jsxNameRe = /^h([1-6])$/
+
 const remarkLintNoDuplicateHeadings = lintRule(
   {
     origin: 'remark-lint:no-duplicate-headings',
@@ -90,22 +107,30 @@ const remarkLintNoDuplicateHeadings = lintRule(
     /** @type {Map<string, string>} */
     const map = new Map()
 
-    visit(tree, 'heading', function (node) {
-      const place = position(node)
-      const start = pointStart(node)
+    visit(tree, function (node) {
+      if (
+        node.type === 'heading' ||
+        ((node.type === 'mdxJsxFlowElement' ||
+          node.type === 'mdxJsxTextElement') &&
+          node.name &&
+          jsxNameRe.test(node.name))
+      ) {
+        const place = position(node)
+        const start = pointStart(node)
 
-      if (place && start) {
-        const value = toString(node).toUpperCase()
-        const duplicate = map.get(value)
+        if (place && start) {
+          const value = toString(node).toLowerCase()
+          const duplicate = map.get(value)
 
-        if (duplicate) {
-          file.message(
-            'Do not use headings with similar content (' + duplicate + ')',
-            node
-          )
-        }
+          if (duplicate) {
+            file.message(
+              'Do not use headings with similar content (' + duplicate + ')',
+              node
+            )
+          }
 
-        map.set(value, stringifyPosition(start))
+          map.set(value, stringifyPosition(start))
+        }
       }
     })
   }
diff --git a/packages/remark-lint-no-duplicate-headings/package.json b/packages/remark-lint-no-duplicate-headings/package.json
index 136b8da5..ccf97af7 100644
--- a/packages/remark-lint-no-duplicate-headings/package.json
+++ b/packages/remark-lint-no-duplicate-headings/package.json
@@ -32,6 +32,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "mdast-util-to-string": "^4.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
diff --git a/packages/remark-lint-no-duplicate-headings/readme.md b/packages/remark-lint-no-duplicate-headings/readme.md
index 6656afe2..29c6eb97 100644
--- a/packages/remark-lint-no-duplicate-headings/readme.md
+++ b/packages/remark-lint-no-duplicate-headings/readme.md
@@ -179,6 +179,26 @@ No messages.
 5:1-5:29: Do not use headings with similar content (3:1)
 ```
 
+##### `mdx.mdx`
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+MDX is supported too.
+
+<h1>Alpha</h1>
+<h2>Alpha</h2>
+```
+
+###### Out
+
+```text
+4:1-4:15: Do not use headings with similar content (3:1)
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -250,6 +270,8 @@ abide by its terms.
 
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
 
 [npm-install]: https://docs.npmjs.com/cli/install
diff --git a/packages/remark-lint-no-heading-punctuation/index.js b/packages/remark-lint-no-heading-punctuation/index.js
index 5fe5cf5e..c744b427 100644
--- a/packages/remark-lint-no-heading-punctuation/index.js
+++ b/packages/remark-lint-no-heading-punctuation/index.js
@@ -17,9 +17,9 @@
  *
  * ###### Parameters
  *
- * * `options` (`string`, default: `'!,\\.:;?'`)
+ * * `options` (`string`, default: `'!,.:;?'`)
  *   — configuration,
- *   wrapped in `new RegExp('[' + x + ']')` so make sure to escape regexp
+ *   wrapped in `new RegExp('[' + x + ']', 'u')` so make sure to escape regexp
  *   characters
  *
  * ###### Returns
@@ -64,17 +64,33 @@
  *   5:1-5:9: Don’t add a trailing `!` to headings
  *   7:1-7:9: Don’t add a trailing `,` to headings
  *   9:1-9:9: Don’t add a trailing `;` to headings
+ *
+ * @example
+ *   {"label": "input", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   MDX is supported <em>too</em>.
+ *
+ *   <h1>Hi?</h1>
+ *
+ * @example
+ *   {"label": "output", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   3:1-3:13: Don’t add a trailing `?` to headings
  */
 
 /**
  * @typedef {import('mdast').Root} Root
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {toString} from 'mdast-util-to-string'
 import {lintRule} from 'unified-lint-rule'
 import {position} from 'unist-util-position'
 import {visit} from 'unist-util-visit'
 
+const jsxNameRe = /^h([1-6])$/
+
 const remarkLintNoHeadingPunctuation = lintRule(
   {
     origin: 'remark-lint:no-heading-punctuation',
@@ -84,24 +100,34 @@ const remarkLintNoHeadingPunctuation = lintRule(
    * @param {Root} tree
    *   Tree.
    * @param {string | null | undefined} [options]
-   *   Configuration (default: `'!,\\.:;?'`),
-   *   wrapped in `new RegExp('[' + x + ']')` so make sure to double escape
+   *   Configuration (default: `'!,.:;?'`),
+   *   wrapped in `new RegExp('[' + x + ']', 'u')` so make sure to double escape
    *   regexp characters.
    * @returns {undefined}
    *   Nothing.
    */
   function (tree, file, options) {
-    const expression = new RegExp('[' + (options || '!,\\.:;?') + ']')
+    const expression = new RegExp('[' + (options || '!,.:;?') + ']', 'u')
 
-    visit(tree, 'heading', function (node) {
-      const place = position(node)
+    visit(tree, function (node) {
+      if (
+        node.type === 'heading' ||
+        ((node.type === 'mdxJsxFlowElement' ||
+          node.type === 'mdxJsxTextElement') &&
+          node.name &&
+          jsxNameRe.test(node.name))
+      ) {
+        const place = position(node)
 
-      if (place) {
-        const value = toString(node)
-        const tail = value.charAt(value.length - 1)
+        if (place) {
+          const tail = Array.from(toString(node)).at(-1)
 
-        if (expression.test(tail)) {
-          file.message('Don’t add a trailing `' + tail + '` to headings', place)
+          if (tail && expression.test(tail)) {
+            file.message(
+              'Don’t add a trailing `' + tail + '` to headings',
+              place
+            )
+          }
         }
       }
     })
diff --git a/packages/remark-lint-no-heading-punctuation/package.json b/packages/remark-lint-no-heading-punctuation/package.json
index e1ec4d23..ba2a84b4 100644
--- a/packages/remark-lint-no-heading-punctuation/package.json
+++ b/packages/remark-lint-no-heading-punctuation/package.json
@@ -32,6 +32,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "mdast-util-to-string": "^4.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
diff --git a/packages/remark-lint-no-heading-punctuation/readme.md b/packages/remark-lint-no-heading-punctuation/readme.md
index 2fd31c11..f291285c 100644
--- a/packages/remark-lint-no-heading-punctuation/readme.md
+++ b/packages/remark-lint-no-heading-punctuation/readme.md
@@ -125,9 +125,9 @@ Warn when headings end in punctuation.
 
 ###### Parameters
 
-* `options` (`string`, default: `'!,\\.:;?'`)
+* `options` (`string`, default: `'!,.:;?'`)
   — configuration,
-  wrapped in `new RegExp('[' + x + ']')` so make sure to escape regexp
+  wrapped in `new RegExp('[' + x + ']', 'u')` so make sure to escape regexp
   characters
 
 ###### Returns
@@ -188,6 +188,25 @@ No messages.
 9:1-9:9: Don’t add a trailing `;` to headings
 ```
 
+##### `mdx.mdx`
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+MDX is supported <em>too</em>.
+
+<h1>Hi?</h1>
+```
+
+###### Out
+
+```text
+3:1-3:13: Don’t add a trailing `?` to headings
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -259,6 +278,8 @@ abide by its terms.
 
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
 
 [npm-install]: https://docs.npmjs.com/cli/install
diff --git a/packages/remark-lint-no-missing-blank-lines/index.js b/packages/remark-lint-no-missing-blank-lines/index.js
index b043dd94..8e95f5db 100644
--- a/packages/remark-lint-no-missing-blank-lines/index.js
+++ b/packages/remark-lint-no-missing-blank-lines/index.js
@@ -31,7 +31,7 @@
  * ###### Fields
  *
  * * `exceptTightLists` (`boolean`, default: `false`)
- *   — allow tight list items
+ *   — allow omitting blank lines in list items
  *
  * ## Recommendation
  *
@@ -98,9 +98,93 @@
  *   {"name": "tight.md", "config": {"exceptTightLists": true}, "label": "output"}
  *
  *   2:1-2:7: Missing blank line before block node
+ *
+ * @example
+ *   {"name": "containers.md", "label": "input"}
+ *
+ *   > # Alpha
+ *   >
+ *   > Bravo.
+ *
+ *   - charlie.
+ *   - delta.
+ *
+ *   + # Echo
+ *     Foxtrot.
+ * @example
+ *   {"name": "containers.md", "label": "output"}
+ *
+ *   9:3-9:11: Missing blank line before block node
+ *
+ * @example
+ *   {"gfm": true, "label": "input", "name": "gfm.md"}
+ *
+ *   GFM tables and footnotes are also checked[^e]
+ *
+ *   | Alpha   | Bravo |
+ *   | ------- | ----- |
+ *   | Charlie | Delta |
+ *
+ *   [^e]: Echo
+ *   [^f]: Foxtrot.
+ *
+ * @example
+ *   {"gfm": true, "label": "output", "name": "gfm.md"}
+ *
+ *   8:1-8:15: Missing blank line before block node
+ *
+ * @example
+ *   {"label": "input", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   MDX JSX flow elements and expressions are also checked.
+ *
+ *   <Tip kind="info">
+ *     # Alpha
+ *     Bravo.
+ *   </Tip>
+ *   {Math.PI}
+ *
+ * @example
+ *   {"label": "output", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   5:3-5:9: Missing blank line before block node
+ *   7:1-7:10: Missing blank line before block node
+ *
+ * @example
+ *   {"label": "input", "math": true, "name": "math.md"}
+ *
+ *   Math is also checked.
+ *
+ *   $$
+ *   \frac{1}{2}
+ *   $$
+ *   $$
+ *   \frac{2}{3}
+ *   $$
+ *
+ * @example
+ *   {"label": "output", "math": true, "name": "math.md"}
+ *
+ *   6:1-8:3: Missing blank line before block node
+ *
+ * @example
+ *   {"directive": true, "label": "input", "name": "directive.md"}
+ *
+ *   Directives are also checked.
+ *
+ *   ::video{#123}
+ *   :::tip
+ *   Tip!
+ *   :::
+ *
+ * @example
+ *   {"directive": true, "label": "output", "name": "directive.md"}
+ *
+ *   4:1-6:4: Missing blank line before block node
  */
 
 /**
+ * @typedef {import('mdast').Nodes} Nodes
  * @typedef {import('mdast').Root} Root
  */
 
@@ -111,21 +195,36 @@
  *   Allow tight list items (default: `false`).
  */
 
+/// <reference types="mdast-util-directive" />
+/// <reference types="mdast-util-math" />
+/// <reference types="mdast-util-mdx" />
+
 import {lintRule} from 'unified-lint-rule'
 import {pointEnd, pointStart} from 'unist-util-position'
 import {visit} from 'unist-util-visit'
 
-const types = new Set([
-  'paragraph',
-  'heading',
-  'thematicBreak',
+/** @type {ReadonlyArray<Nodes['type']>} */
+// eslint-disable-next-line unicorn/prefer-set-has
+const types = [
   'blockquote',
+  'code',
+  'containerDirective',
+  'definition',
+  'footnoteDefinition',
+  'heading',
+  'html',
+  'leafDirective',
   'list',
+  'math',
+  'mdxFlowExpression',
+  'mdxJsxFlowElement',
+  'paragraph',
   'table',
-  'html',
-  'code',
+  'thematicBreak',
+  // @ts-expect-error: `remark-frontmatter`.
+  'toml',
   'yaml'
-])
+]
 
 const remarkLintNoMissingBlankLines = lintRule(
   {
@@ -144,24 +243,23 @@ const remarkLintNoMissingBlankLines = lintRule(
     const exceptTightLists = options ? options.exceptTightLists : false
 
     visit(tree, function (node, index, parent) {
-      const end = pointEnd(node)
-
       if (
         parent &&
         typeof index === 'number' &&
-        end &&
-        (!exceptTightLists || parent.type !== 'listItem')
+        types.includes(node.type) &&
+        (parent.type !== 'listItem' || !exceptTightLists)
       ) {
-        const next = parent.children[index + 1]
-        const nextPoint = pointStart(next)
+        const start = pointStart(node)
+        const previous = parent.children[index - 1]
+        const previousEnd = pointEnd(previous)
 
         if (
-          next &&
-          nextPoint &&
-          types.has(next.type) &&
-          nextPoint.line === end.line + 1
+          start &&
+          previousEnd &&
+          types.includes(previous.type) &&
+          start.line === previousEnd.line + 1
         ) {
-          file.message('Missing blank line before block node', next)
+          file.message('Missing blank line before block node', node)
         }
       }
     })
diff --git a/packages/remark-lint-no-missing-blank-lines/package.json b/packages/remark-lint-no-missing-blank-lines/package.json
index 179a4cee..6f29520b 100644
--- a/packages/remark-lint-no-missing-blank-lines/package.json
+++ b/packages/remark-lint-no-missing-blank-lines/package.json
@@ -32,6 +32,9 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-directive": "^3.0.0",
+    "mdast-util-math": "^3.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
     "unist-util-visit": "^5.0.0"
diff --git a/packages/remark-lint-no-missing-blank-lines/readme.md b/packages/remark-lint-no-missing-blank-lines/readme.md
index 6321b995..252d828c 100644
--- a/packages/remark-lint-no-missing-blank-lines/readme.md
+++ b/packages/remark-lint-no-missing-blank-lines/readme.md
@@ -139,7 +139,7 @@ Configuration (TypeScript type).
 ###### Fields
 
 * `exceptTightLists` (`boolean`, default: `false`)
-  — allow tight list items
+  — allow omitting blank lines in list items
 
 ## Recommendation
 
@@ -217,6 +217,122 @@ Paragraph.
 2:1-2:7: Missing blank line before block node
 ```
 
+##### `containers.md`
+
+###### In
+
+```markdown
+> # Alpha
+>
+> Bravo.
+
+- charlie.
+- delta.
+
++ # Echo
+  Foxtrot.
+```
+
+###### Out
+
+```text
+9:3-9:11: Missing blank line before block node
+```
+
+##### `gfm.md`
+
+###### In
+
+> 👉 **Note**: this example uses
+> GFM ([`remark-gfm`][github-remark-gfm]).
+
+```markdown
+GFM tables and footnotes are also checked[^e]
+
+| Alpha   | Bravo |
+| ------- | ----- |
+| Charlie | Delta |
+
+[^e]: Echo
+[^f]: Foxtrot.
+```
+
+###### Out
+
+```text
+8:1-8:15: Missing blank line before block node
+```
+
+##### `mdx.mdx`
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+MDX JSX flow elements and expressions are also checked.
+
+<Tip kind="info">
+  # Alpha
+  Bravo.
+</Tip>
+{Math.PI}
+```
+
+###### Out
+
+```text
+5:3-5:9: Missing blank line before block node
+7:1-7:10: Missing blank line before block node
+```
+
+##### `math.md`
+
+###### In
+
+> 👉 **Note**: this example uses
+> math ([`remark-math`][github-remark-math]).
+
+```markdown
+Math is also checked.
+
+$$
+\frac{1}{2}
+$$
+$$
+\frac{2}{3}
+$$
+```
+
+###### Out
+
+```text
+6:1-8:3: Missing blank line before block node
+```
+
+##### `directive.md`
+
+###### In
+
+> 👉 **Note**: this example uses
+> directives ([`remark-directive`][github-remark-directive]).
+
+```markdown
+Directives are also checked.
+
+::video{#123}
+:::tip
+Tip!
+:::
+```
+
+###### Out
+
+```text
+4:1-6:4: Missing blank line before block node
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -288,8 +404,16 @@ abide by its terms.
 
 [github-gist-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
 
+[github-remark-directive]: https://github.com/remarkjs/remark-directive
+
+[github-remark-gfm]: https://github.com/remarkjs/remark-gfm
+
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-math]: https://github.com/remarkjs/remark-math
+
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-remark-stringify]: https://github.com/remarkjs/remark/tree/main/packages/remark-stringify
 
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
diff --git a/packages/remark-lint-no-multiple-toplevel-headings/index.js b/packages/remark-lint-no-multiple-toplevel-headings/index.js
index bb127fe7..aff1004e 100644
--- a/packages/remark-lint-no-multiple-toplevel-headings/index.js
+++ b/packages/remark-lint-no-multiple-toplevel-headings/index.js
@@ -24,6 +24,16 @@
  *
  * Transform ([`Transformer` from `unified`][github-unified-transformer]).
  *
+ * ### `Depth`
+ *
+ * Depth (TypeScript type).
+ *
+ * ###### Type
+ *
+ * ```ts
+ * type Depth = 1 | 2 | 3 | 4 | 5 | 6
+ * ```
+ *
  * ### `Options`
  *
  * Configuration (TypeScript type).
@@ -31,7 +41,7 @@
  * ###### Type
  *
  * ```ts
- * type Options = 1 | 2 | 3 | 4 | 5 | 6
+ * type Options = Depth
  * ```
  *
  * ## Recommendation
@@ -39,6 +49,7 @@
  * Documents should almost always have one main heading,
  * which is typically a heading with a rank of `1`.
  *
+ * [api-depth]: #depth
  * [api-options]: #options
  * [api-remark-lint-no-multiple-toplevel-headings]: #unifieduseremarklintnomultipletoplevelheadings-options
  * [github-remark-stringify]: https://github.com/remarkjs/remark/tree/main/packages/remark-stringify
@@ -66,6 +77,31 @@
  *   {"name": "not-ok.md", "config": 1, "label": "output"}
  *
  *   3:1-3:6: Don’t use multiple top level headings (1:1)
+ *
+ * @example
+ *   {"label": "input", "name": "html.md"}
+ *
+ *   In markdown, <b>HTML</b> is supported.
+ *
+ *   <h1>First</h1>
+ *
+ *   <h1>Second</h1>
+ * @example
+ *   {"label": "output", "name": "html.md"}
+ *
+ *   5:1-5:16: Don’t use multiple top level headings (3:1)
+ *
+ * @example
+ *   {"label": "input", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   In MDX, <b>JSX</b> is supported.
+ *
+ *   <h1>First</h1>
+ *   <h1>Second</h1>
+ * @example
+ *   {"label": "output", "mdx": true, "name": "mdx.mdx"}
+ *
+ *   4:1-4:16: Don’t use multiple top level headings (3:1)
  */
 
 /**
@@ -74,15 +110,23 @@
  */
 
 /**
- * @typedef {Heading['depth']} Options
+ * @typedef {Heading['depth']} Depth
+ *   Styles.
+ *
+ * @typedef {Depth} Options
  *   Configuration.
  */
 
+/// <reference types="mdast-util-mdx" />
+
 import {lintRule} from 'unified-lint-rule'
 import {pointStart, position} from 'unist-util-position'
 import {stringifyPosition} from 'unist-util-stringify-position'
 import {visit} from 'unist-util-visit'
 
+const htmlRe = /<h([1-6])/
+const jsxNameRe = /^h([1-6])$/
+
 const remarkLintNoMultipleToplevelHeadings = lintRule(
   {
     origin: 'remark-lint:no-multiple-toplevel-headings',
@@ -101,18 +145,37 @@ const remarkLintNoMultipleToplevelHeadings = lintRule(
     /** @type {string | undefined} */
     let duplicate
 
-    visit(tree, 'heading', function (node) {
-      const start = pointStart(node)
-      const place = position(node)
+    visit(tree, function (node) {
+      /** @type {Depth | undefined} */
+      let rank
+
+      if (node.type === 'heading') {
+        rank = node.depth
+      } else if (node.type === 'html') {
+        const results = node.value.match(htmlRe)
+        rank = results ? /** @type {Depth} */ (Number(results[1])) : undefined
+      } else if (
+        (node.type === 'mdxJsxFlowElement' ||
+          node.type === 'mdxJsxTextElement') &&
+        node.name
+      ) {
+        const results = node.name.match(jsxNameRe)
+        rank = results ? /** @type {Depth} */ (Number(results[1])) : undefined
+      }
+
+      if (rank) {
+        const start = pointStart(node)
+        const place = position(node)
 
-      if (start && place && node.depth === option) {
-        if (duplicate) {
-          file.message(
-            'Don’t use multiple top level headings (' + duplicate + ')',
-            place
-          )
-        } else {
-          duplicate = stringifyPosition(start)
+        if (start && place && rank === option) {
+          if (duplicate) {
+            file.message(
+              'Don’t use multiple top level headings (' + duplicate + ')',
+              place
+            )
+          } else {
+            duplicate = stringifyPosition(start)
+          }
         }
       }
     })
diff --git a/packages/remark-lint-no-multiple-toplevel-headings/package.json b/packages/remark-lint-no-multiple-toplevel-headings/package.json
index 067ba0dd..a1241fc8 100644
--- a/packages/remark-lint-no-multiple-toplevel-headings/package.json
+++ b/packages/remark-lint-no-multiple-toplevel-headings/package.json
@@ -32,6 +32,7 @@
   ],
   "dependencies": {
     "@types/mdast": "^4.0.0",
+    "mdast-util-mdx": "^3.0.0",
     "unified-lint-rule": "^2.0.0",
     "unist-util-position": "^5.0.0",
     "unist-util-stringify-position": "^4.0.0",
diff --git a/packages/remark-lint-no-multiple-toplevel-headings/readme.md b/packages/remark-lint-no-multiple-toplevel-headings/readme.md
index 469d7265..2543b478 100644
--- a/packages/remark-lint-no-multiple-toplevel-headings/readme.md
+++ b/packages/remark-lint-no-multiple-toplevel-headings/readme.md
@@ -21,6 +21,7 @@
 * [Use](#use)
 * [API](#api)
   * [`unified().use(remarkLintNoMultipleToplevelHeadings[, options])`](#unifieduseremarklintnomultipletoplevelheadings-options)
+  * [`Depth`](#depth)
   * [`Options`](#options)
 * [Recommendation](#recommendation)
 * [Examples](#examples)
@@ -117,7 +118,8 @@ On the CLI in a config file (here a `package.json`):
 ## API
 
 This package exports no identifiers.
-It exports the [TypeScript][typescript] type
+It exports the [TypeScript][typescript] types
+[`Depth`][api-depth] and
 [`Options`][api-options].
 The default export is
 [`remarkLintNoMultipleToplevelHeadings`][api-remark-lint-no-multiple-toplevel-headings].
@@ -135,6 +137,16 @@ Warn when multiple top-level headings are used.
 
 Transform ([`Transformer` from `unified`][github-unified-transformer]).
 
+### `Depth`
+
+Depth (TypeScript type).
+
+###### Type
+
+```ts
+type Depth = 1 | 2 | 3 | 4 | 5 | 6
+```
+
 ### `Options`
 
 Configuration (TypeScript type).
@@ -142,7 +154,7 @@ Configuration (TypeScript type).
 ###### Type
 
 ```ts
-type Options = 1 | 2 | 3 | 4 | 5 | 6
+type Options = Depth
 ```
 
 ## Recommendation
@@ -186,6 +198,44 @@ When configured with `1`.
 3:1-3:6: Don’t use multiple top level headings (1:1)
 ```
 
+##### `html.md`
+
+###### In
+
+```markdown
+In markdown, <b>HTML</b> is supported.
+
+<h1>First</h1>
+
+<h1>Second</h1>
+```
+
+###### Out
+
+```text
+5:1-5:16: Don’t use multiple top level headings (3:1)
+```
+
+##### `mdx.mdx`
+
+###### In
+
+> 👉 **Note**: this example uses
+> MDX ([`remark-mdx`][github-remark-mdx]).
+
+```mdx
+In MDX, <b>JSX</b> is supported.
+
+<h1>First</h1>
+<h1>Second</h1>
+```
+
+###### Out
+
+```text
+4:1-4:16: Don’t use multiple top level headings (3:1)
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -211,6 +261,8 @@ abide by its terms.
 
 [MIT][file-license] © [Titus Wormer][author]
 
+[api-depth]: #depth
+
 [api-options]: #options
 
 [api-remark-lint-no-multiple-toplevel-headings]: #unifieduseremarklintnomultipletoplevelheadings-options
@@ -259,6 +311,8 @@ abide by its terms.
 
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
+[github-remark-mdx]: https://mdxjs.com/packages/remark-mdx/
+
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
 
 [npm-install]: https://docs.npmjs.com/cli/install
diff --git a/packages/remark-lint-no-undefined-references/index.js b/packages/remark-lint-no-undefined-references/index.js
index 2c8e54d1..da0a1037 100644
--- a/packages/remark-lint-no-undefined-references/index.js
+++ b/packages/remark-lint-no-undefined-references/index.js
@@ -80,12 +80,12 @@
  *   [foo]: https://example.com
  *
  * @example
- *   {"name": "ok-allow.md", "config": {"allow": ["...", "…"]}}
+ *   {"config": {"allow": ["…"]}, "name": "ok-allow.md"}
  *
  *   > Eliding a portion of a quoted passage […] is acceptable.
  *
  * @example
- *   {"name": "ok-allow.md", "config": {"allow": ["a", {"source": "^b\\."}]}}
+ *   {"config": {"allow": ["a", {"source": "^b\\."}]}, "name": "ok-allow-source.md"}
  *
  *   [foo][b.c]
  *
@@ -94,7 +94,7 @@
  *   Matching is case-insensitive: [bar][B.C]
  *
  * @example
- *   {"name": "not-ok.md", "label": "input"}
+ *   {"label": "input", "name": "not-ok.md"}
  *
  *   [bar]
  *
@@ -113,9 +113,8 @@
  *   Can include [*emphasis*].
  *
  *   Multiple pairs: [a][b][c].
- *
  * @example
- *   {"name": "not-ok.md", "label": "output"}
+ *   {"label": "output", "name": "not-ok.md"}
  *
  *   1:1-1:6: Found reference to undefined definition
  *   3:1-3:8: Found reference to undefined definition
@@ -128,17 +127,27 @@
  *   17:23-17:26: Found reference to undefined definition
  *
  * @example
- *   {"name": "not-ok.md", "label": "input", "config": {"allow": ["a", {"source": "^b\\."}]}}
+ *   {"config": {"allow": ["a", {"source": "^b\\."}]}, "label": "input", "name": "not-ok-source.md"}
  *
  *   [foo][a.c]
  *
  *   [bar][b]
- *
  * @example
- *   {"name": "not-ok.md", "label": "output", "config": {"allow": ["a", {"source": "^b\\."}]}}
+ *   {"config": {"allow": ["a", {"source": "^b\\."}]}, "label": "output", "name": "not-ok-source.md"}
  *
  *   1:1-1:11: Found reference to undefined definition
  *   3:1-3:9: Found reference to undefined definition
+ *
+ * @example
+ *   {"gfm": true, "label": "input", "name": "gfm.md"}
+ *
+ *   GFM footnote calls are supported too.
+ *
+ *   Alpha[^a]
+ * @example
+ *   {"gfm": true, "label": "output", "name": "gfm.md"}
+ *
+ *   3:6-3:10: Found reference to undefined definition
  */
 
 /**
@@ -150,7 +159,7 @@
 /**
  * @typedef Options
  *   Configuration.
- * @property {Readonly<Array<RegExp | {source: string} | string>> | null | undefined} [allow]
+ * @property {ReadonlyArray<{source: string} | RegExp | string> | null | undefined} [allow]
  *   Text or regexes to allow between `[` and `]` even though they’re not
  *   defined (optional).
  */
@@ -163,7 +172,7 @@ import {location} from 'vfile-location'
 
 /** @type {Readonly<Options>} */
 const emptyOptions = {}
-/** @type {Readonly<Array<RegExp | {source: string} | string>>} */
+/** @type {ReadonlyArray<{source: string} | RegExp | string>} */
 const emptyAllow = []
 
 const remarkLintNoUndefinedReferences = lintRule(
@@ -196,6 +205,7 @@ const remarkLintNoUndefinedReferences = lintRule(
 
     while (++index < allow.length) {
       const value = allow[index]
+
       if (typeof value === 'string') {
         strings.add(normalizeIdentifier(value))
       } else if (value instanceof RegExp) {
@@ -213,6 +223,7 @@ const remarkLintNoUndefinedReferences = lintRule(
 
     visit(tree, function (node) {
       const place = position(node)
+
       /* c8 ignore next 12 -- CM specifies that references only form when
        * defined.
        * Still, they could be added by plugins, so let’s keep it. */
@@ -227,7 +238,7 @@ const remarkLintNoUndefinedReferences = lintRule(
         file.message('Found reference to undefined definition', place)
       }
 
-      if (node.type === 'paragraph' || node.type === 'heading') {
+      if (node.type === 'heading' || node.type === 'paragraph') {
         findInPhrasing(node)
         return SKIP
       }
diff --git a/packages/remark-lint-no-undefined-references/readme.md b/packages/remark-lint-no-undefined-references/readme.md
index 5dd3e72f..5ed52d9d 100644
--- a/packages/remark-lint-no-undefined-references/readme.md
+++ b/packages/remark-lint-no-undefined-references/readme.md
@@ -193,7 +193,7 @@ No messages.
 
 ##### `ok-allow.md`
 
-When configured with `{ allow: [ '...', '…' ] }`.
+When configured with `{ allow: [ '…' ] }`.
 
 ###### In
 
@@ -205,7 +205,7 @@ When configured with `{ allow: [ '...', '…' ] }`.
 
 No messages.
 
-##### `ok-allow.md`
+##### `ok-allow-source.md`
 
 When configured with `{ allow: [ 'a', { source: '^b\\.' } ] }`.
 
@@ -261,7 +261,7 @@ Multiple pairs: [a][b][c].
 17:23-17:26: Found reference to undefined definition
 ```
 
-##### `not-ok.md`
+##### `not-ok-source.md`
 
 When configured with `{ allow: [ 'a', { source: '^b\\.' } ] }`.
 
@@ -280,6 +280,25 @@ When configured with `{ allow: [ 'a', { source: '^b\\.' } ] }`.
 3:1-3:9: Found reference to undefined definition
 ```
 
+##### `gfm.md`
+
+###### In
+
+> 👉 **Note**: this example uses
+> GFM ([`remark-gfm`][github-remark-gfm]).
+
+```markdown
+GFM footnote calls are supported too.
+
+Alpha[^a]
+```
+
+###### Out
+
+```text
+3:6-3:10: Found reference to undefined definition
+```
+
 ## Compatibility
 
 Projects maintained by the unified collective are compatible with maintained
@@ -351,6 +370,8 @@ abide by its terms.
 
 [github-gist-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
 
+[github-remark-gfm]: https://github.com/remarkjs/remark-gfm
+
 [github-remark-lint]: https://github.com/remarkjs/remark-lint
 
 [github-unified-transformer]: https://github.com/unifiedjs/unified#transformer
diff --git a/packages/remark-lint-no-unused-definitions/index.js b/packages/remark-lint-no-unused-definitions/index.js
index 3884e475..875b8e5c 100644
--- a/packages/remark-lint-no-unused-definitions/index.js
+++ b/packages/remark-lint-no-unused-definitions/index.js
@@ -52,7 +52,7 @@
  *   1:1-1:27: Found unused definition
  *
  * @example
- *   {"name": "footnote.md", "gfm": true, "label": "input"}
+ *   {"gfm": true, "label": "input", "name": "gfm.md"}
  *
  *   a[^x].
  *
@@ -60,7 +60,7 @@
  *   [^y]: not ok
  *
  * @example
- *   {"name": "footnote.md", "gfm": true, "label": "output"}
+ *   {"gfm": true, "label": "output", "name": "gfm.md"}
  *
  *   4:1-4:13: Found unused footnote definition
  */
diff --git a/packages/remark-lint-no-unused-definitions/readme.md b/packages/remark-lint-no-unused-definitions/readme.md
index ba56b3af..8119f847 100644
--- a/packages/remark-lint-no-unused-definitions/readme.md
+++ b/packages/remark-lint-no-unused-definitions/readme.md
@@ -166,7 +166,7 @@ No messages.
 1:1-1:27: Found unused definition
 ```
 
-##### `footnote.md`
+##### `gfm.md`
 
 ###### In
 
diff --git a/script/info.js b/script/info.js
index 3947f691..bc61cacd 100644
--- a/script/info.js
+++ b/script/info.js
@@ -8,10 +8,14 @@
  *   Check.
  * @property {string} configuration
  *   Configuration.
+ * @property {boolean} directive
+ *   Whether to use directives.
  * @property {boolean} gfm
  *   Whether to use GFM.
  * @property {string} input
  *   Input.
+ * @property {boolean} math
+ *   Whether to use math.
  * @property {boolean} mdx
  *   Whether to use MDX.
  * @property {string} name
@@ -25,10 +29,14 @@
  *   Example.
  * @property {unknown} [config]
  *   Configuration (optional).
+ * @property {boolean} [directive]
+ *   Whether to use directives.
  * @property {boolean} [gfm]
  *   Whether to use GFM (optional).
  * @property {'input' | 'output'} [label]
  *   Label (optional).
+ * @property {boolean} [math]
+ *   Whether to use math.
  * @property {boolean} [mdx]
  *   Whether to use MDX (optional).
  * @property {boolean} [positionless]
@@ -173,12 +181,14 @@ async function addPlugin(name) {
     if (!info.label) {
       result.checks.push({
         configuration,
-        name,
-        positionless: info.positionless || false,
+        directive: info.directive || false,
         gfm: info.gfm || false,
         input: exampleValue,
+        math: info.math || false,
         mdx: info.mdx || false,
-        output: []
+        name,
+        output: [],
+        positionless: info.positionless || false
       })
 
       continue
@@ -193,12 +203,14 @@ async function addPlugin(name) {
     if (!found) {
       found = {
         configuration,
-        name,
-        positionless: info.positionless || false,
+        directive: info.directive || false,
         gfm: info.gfm || false,
         input: '',
+        math: info.math || false,
         mdx: info.mdx || false,
-        output: []
+        name,
+        output: [],
+        positionless: info.positionless || false
       }
       result.checks.push(found)
     }
diff --git a/script/pipeline-package.js b/script/pipeline-package.js
index c940ca48..54320799 100644
--- a/script/pipeline-package.js
+++ b/script/pipeline-package.js
@@ -1252,10 +1252,18 @@ function generateReadmeExample(state) {
 
     const empty = check.input.trim() === ''
 
+    state.urls.set(
+      'github-remark-directive',
+      'https://github.com/remarkjs/remark-directive'
+    )
     state.urls.set(
       'github-remark-gfm',
       'https://github.com/remarkjs/remark-gfm'
     )
+    state.urls.set(
+      'github-remark-math',
+      'https://github.com/remarkjs/remark-math'
+    )
     state.urls.set(
       'github-remark-mdx',
       'https://mdxjs.com/packages/remark-mdx/'
@@ -1271,7 +1279,28 @@ function generateReadmeExample(state) {
       /** @type {Array<PhrasingContent>} */
       const phrasing = []
 
+      if (check.directive) {
+        if (phrasing.length > 0) {
+          phrasing.push({type: 'text', value: ',\n'})
+        }
+
+        phrasing.push(
+          {type: 'text', value: 'directives ('},
+          {
+            type: 'linkReference',
+            identifier: 'github-remark-directive',
+            referenceType: 'full',
+            children: [{type: 'inlineCode', value: 'remark-directive'}]
+          },
+          {type: 'text', value: ')'}
+        )
+      }
+
       if (check.gfm) {
+        if (phrasing.length > 0) {
+          phrasing.push({type: 'text', value: ',\n'})
+        }
+
         phrasing.push(
           {type: 'text', value: 'GFM ('},
           {
@@ -1284,6 +1313,23 @@ function generateReadmeExample(state) {
         )
       }
 
+      if (check.math) {
+        if (phrasing.length > 0) {
+          phrasing.push({type: 'text', value: ',\n'})
+        }
+
+        phrasing.push(
+          {type: 'text', value: 'math ('},
+          {
+            type: 'linkReference',
+            identifier: 'github-remark-math',
+            referenceType: 'full',
+            children: [{type: 'inlineCode', value: 'remark-math'}]
+          },
+          {type: 'text', value: ')'}
+        )
+      }
+
       if (check.mdx) {
         if (phrasing.length > 0) {
           phrasing.push({type: 'text', value: ',\n'})
diff --git a/test.js b/test.js
index 6c8c40e1..366be95d 100644
--- a/test.js
+++ b/test.js
@@ -10,12 +10,14 @@ import assert from 'node:assert/strict'
 import test from 'node:test'
 import {controlPictures} from 'control-pictures'
 import {remark} from 'remark'
+import remarkDirective from 'remark-directive'
 import remarkGfm from 'remark-gfm'
 import remarkLint from 'remark-lint'
 import remarkLintFinalNewline from 'remark-lint-final-newline'
 import remarkLintNoHeadingPunctuation from 'remark-lint-no-heading-punctuation'
 import remarkLintNoMultipleToplevelHeadings from 'remark-lint-no-multiple-toplevel-headings'
 import remarkLintNoUndefinedReferences from 'remark-lint-no-undefined-references'
+import remarkMath from 'remark-math'
 import remarkMdx from 'remark-mdx'
 import {lintRule} from 'unified-lint-rule'
 import {removePosition} from 'unist-util-remove-position'
@@ -318,13 +320,10 @@ async function assertCheck(plugin, info, check) {
   const extras = []
   const value = controlPictures(check.input)
 
-  if (check.gfm) {
-    extras.push(remarkGfm)
-  }
-
-  if (check.mdx) {
-    extras.push(remarkMdx)
-  }
+  if (check.directive) extras.push(remarkDirective)
+  if (check.gfm) extras.push(remarkGfm)
+  if (check.math) extras.push(remarkMath)
+  if (check.mdx) extras.push(remarkMdx)
 
   const file = await remark()
     .use(plugin, config)
diff --git a/tsconfig.json b/tsconfig.json
index 9212b256..ac7feb00 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,7 +6,7 @@
     "declarationMap": true,
     "emitDeclarationOnly": true,
     "exactOptionalPropertyTypes": true,
-    "lib": ["es2022"],
+    "lib": ["dom", "es2022"],
     "module": "node16",
     "strict": true,
     "target": "es2020"