diff --git a/lib/rules/selector-max-specificity/index.cjs b/lib/rules/selector-max-specificity/index.cjs
index ca0ac359f0..86c60b7a10 100644
--- a/lib/rules/selector-max-specificity/index.cjs
+++ b/lib/rules/selector-max-specificity/index.cjs
@@ -3,7 +3,6 @@
 'use strict';
 
 const selectorSpecificity = require('@csstools/selector-specificity');
-const selectors = require('../../reference/selectors.cjs');
 const validateTypes = require('../../utils/validateTypes.cjs');
 const flattenNestedSelectorsForRule = require('../../utils/flattenNestedSelectorsForRule.cjs');
 const isStandardSyntaxRule = require('../../utils/isStandardSyntaxRule.cjs');
@@ -31,24 +30,6 @@ const meta = {
  */
 const zeroSpecificity = () => ({ a: 0, b: 0, c: 0 });
 
-/**
- * Calculate the sum of given specificities.
- *
- * @param {Specificity[]} specificities
- * @returns {Specificity}
- */
-const specificitySum = (specificities) => {
-	const sum = zeroSpecificity();
-
-	for (const { a, b, c } of specificities) {
-		sum.a += a;
-		sum.b += b;
-		sum.c += c;
-	}
-
-	return sum;
-};
-
 /** @type {import('stylelint').Rule<string>} */
 const rule = (primary, secondaryOptions) => {
 	return (root, result) => {
@@ -79,148 +60,45 @@ const rule = (primary, secondaryOptions) => {
 		const isSelectorIgnored = (selector) =>
 			optionsMatches(secondaryOptions, 'ignoreSelectors', selector);
 
-		/**
-		 * Calculate the specificity of a simple selector (type, attribute, class, ID, or pseudos's own value).
-		 *
-		 * @param {import('postcss-selector-parser').Node} node
-		 * @returns {Specificity}
-		 */
-		const simpleSpecificity = (node) => {
-			if (isSelectorIgnored(node.toString())) {
-				return zeroSpecificity();
-			}
-
-			return selectorSpecificity.selectorSpecificity(node);
-		};
-
-		/**
-		 * Calculate the specificity of the most specific direct child.
-		 *
-		 * @param {import('postcss-selector-parser').Container<string | undefined>} node
-		 * @returns {Specificity}
-		 */
-		const maxChildSpecificity = (node) =>
-			node.reduce((maxSpec, child) => {
-				const childSpecificity = nodeSpecificity(child); // eslint-disable-line no-use-before-define
-
-				return selectorSpecificity.compare(childSpecificity, maxSpec) > 0 ? childSpecificity : maxSpec;
-			}, zeroSpecificity());
-
-		/**
-		 * If a `of <selector>` (`An+B of S`) is found in the specified pseudo node,
-		 * returns a copy of the pseudo node, ignoring a `of` selector (`An+B of S`).
-		 * Otherwise, returns the specified node as-is.
-		 *
-		 * @see https://drafts.csswg.org/selectors/#the-nth-child-pseudo
-		 * @param {import('postcss-selector-parser').Pseudo} pseudo
-		 * @returns {import('postcss-selector-parser').Pseudo}
-		 */
-		const ignoreOfSelectorIfAny = (pseudo) => {
-			/** @type {(node: import('postcss-selector-parser').Node | undefined) => boolean} */
-			const isOfSelector = (node) => node?.type === 'tag' && node.value === 'of';
-
-			/** @type {(node: import('postcss-selector-parser').Node | undefined) => boolean} */
-			const isSpace = (node) => node?.type === 'combinator' && node.value === ' ';
-
-			const nodes = pseudo.nodes[0]?.nodes ?? [];
-			const ofSelectorIndex = nodes.findIndex((child, i, children) => {
-				// Find ' of <selector>' nodes
-				return isSpace(child) && isOfSelector(children[i + 1]) && isSpace(children[i + 2]);
-			});
-
-			const ofSelector = nodes[ofSelectorIndex + 3];
-
-			if (!ofSelector || !ofSelector.value) return pseudo;
-
-			if (!isSelectorIgnored(ofSelector.value)) return pseudo;
-
-			const copy = pseudo.clone();
-			const rootSelector = copy.nodes[0];
-
-			if (rootSelector) {
-				// Remove ' of <selector>' nodes
-				rootSelector.nodes = rootSelector.nodes.slice(0, ofSelectorIndex);
-			}
-
-			return copy;
-		};
-
-		/**
-		 * Calculate the specificity of a pseudo selector including own value and children.
-		 *
-		 * @param {import('postcss-selector-parser').Pseudo} node
-		 * @returns {Specificity}
-		 */
-		const pseudoSpecificity = (node) => {
-			// `node.toString()` includes children which should be processed separately,
-			// so use `node.value` instead
-			const ownValue = node.value.toLowerCase();
-
-			if (ownValue === ':where') {
-				return zeroSpecificity();
-			}
-
-			let ownSpecificity;
-
-			if (isSelectorIgnored(ownValue)) {
-				ownSpecificity = zeroSpecificity();
-			} else if (selectors.aNPlusBOfSNotationPseudoClasses.has(ownValue.replace(/^:/, ''))) {
-				return selectorSpecificity.selectorSpecificity(ignoreOfSelectorIfAny(node));
-			} else {
-				ownSpecificity = selectorSpecificity.selectorSpecificity(node.clone({ nodes: [] }));
-			}
-
-			return specificitySum([ownSpecificity, maxChildSpecificity(node)]);
-		};
-
-		/**
-		 * @param {import('postcss-selector-parser').Node} node
-		 * @returns {boolean}
-		 */
-		const shouldSkipPseudoClassArgument = (node) => {
-			// postcss-selector-parser includes the arguments to nth-child() functions
-			// as "tags", so we need to ignore them ourselves.
-			// The fake-tag's "parent" is actually a selector node, whose parent
-			// should be the :nth-child pseudo node.
-			const parentNode = node.parent && node.parent.parent;
-
-			if (parentNode && parentNode.type === 'pseudo' && parentNode.value) {
-				const pseudoClass = parentNode.value.toLowerCase().replace(/^:/, '');
-
-				return (
-					selectors.aNPlusBNotationPseudoClasses.has(pseudoClass) || selectors.linguisticPseudoClasses.has(pseudoClass)
-				);
-			}
-
-			return false;
-		};
-
-		/**
-		 * Calculate the specificity of a node parsed by `postcss-selector-parser`.
-		 *
-		 * @param {import('postcss-selector-parser').Node} node
-		 * @returns {Specificity}
-		 */
-		const nodeSpecificity = (node) => {
-			if (shouldSkipPseudoClassArgument(node)) {
-				return zeroSpecificity();
-			}
-
-			switch (node.type) {
-				case 'attribute':
-				case 'class':
-				case 'id':
-				case 'tag':
-					return simpleSpecificity(node);
-				case 'pseudo':
-					return pseudoSpecificity(node);
-				case 'selector':
-					// Calculate the sum of all the direct children
-					return specificitySum(node.map((n) => nodeSpecificity(n)));
-				default:
-					return zeroSpecificity();
-			}
-		};
+		/** @type {import('@csstools/selector-specificity').CustomSpecificityCallback | undefined} */
+		const customSpecificity = secondaryOptions?.ignoreSelectors
+			? (node) => {
+					switch (node.type) {
+						case 'attribute':
+						case 'class':
+						case 'id':
+						case 'tag':
+							if (!isSelectorIgnored(node.toString())) {
+								return;
+							}
+
+							return zeroSpecificity();
+						case 'pseudo': {
+							if (!isSelectorIgnored(node.value.toLowerCase())) {
+								return;
+							}
+
+							if (!node.nodes?.length) {
+								return zeroSpecificity();
+							}
+
+							// We only ignore the current pseudo-class, not the specificity of the child nodes.
+							// Calculate the diff between specificity with and without child nodes.
+							const entireSpecificity = selectorSpecificity.selectorSpecificity(node);
+
+							const emptySpecificity = selectorSpecificity.selectorSpecificity(node.clone({ nodes: [] }));
+
+							return {
+								a: entireSpecificity.a - emptySpecificity.a,
+								b: entireSpecificity.b - emptySpecificity.b,
+								c: entireSpecificity.c - emptySpecificity.c,
+							};
+						}
+						default:
+						// Other node types are not ignorable.
+					}
+			  }
+			: undefined;
 
 		const [a, b, c] = primary.split(',').map((s) => Number.parseFloat(s));
 
@@ -235,8 +113,10 @@ const rule = (primary, secondaryOptions) => {
 
 			flattenNestedSelectorsForRule(ruleNode, result).forEach(({ selector, resolvedSelectors }) => {
 				resolvedSelectors.forEach((resolvedSelector) => {
+					const specificity = selectorSpecificity.selectorSpecificity(resolvedSelector, { customSpecificity });
+
 					// Check if the selector specificity exceeds the allowed maximum
-					if (selectorSpecificity.compare(nodeSpecificity(resolvedSelector), maxSpecificity) > 0) {
+					if (selectorSpecificity.compare(specificity, maxSpecificity) > 0) {
 						const index = selector.first?.sourceIndex ?? 0;
 						const selectorStr = selector.toString().trim();
 
diff --git a/lib/rules/selector-max-specificity/index.mjs b/lib/rules/selector-max-specificity/index.mjs
index 611d2b40a1..4e3c0c7035 100644
--- a/lib/rules/selector-max-specificity/index.mjs
+++ b/lib/rules/selector-max-specificity/index.mjs
@@ -1,10 +1,5 @@
 import { compare, selectorSpecificity } from '@csstools/selector-specificity';
 
-import {
-	aNPlusBNotationPseudoClasses,
-	aNPlusBOfSNotationPseudoClasses,
-	linguisticPseudoClasses,
-} from '../../reference/selectors.mjs';
 import { assertNumber, isRegExp, isString } from '../../utils/validateTypes.mjs';
 import flattenNestedSelectorsForRule from '../../utils/flattenNestedSelectorsForRule.mjs';
 import isStandardSyntaxRule from '../../utils/isStandardSyntaxRule.mjs';
@@ -32,24 +27,6 @@ const meta = {
  */
 const zeroSpecificity = () => ({ a: 0, b: 0, c: 0 });
 
-/**
- * Calculate the sum of given specificities.
- *
- * @param {Specificity[]} specificities
- * @returns {Specificity}
- */
-const specificitySum = (specificities) => {
-	const sum = zeroSpecificity();
-
-	for (const { a, b, c } of specificities) {
-		sum.a += a;
-		sum.b += b;
-		sum.c += c;
-	}
-
-	return sum;
-};
-
 /** @type {import('stylelint').Rule<string>} */
 const rule = (primary, secondaryOptions) => {
 	return (root, result) => {
@@ -80,148 +57,45 @@ const rule = (primary, secondaryOptions) => {
 		const isSelectorIgnored = (selector) =>
 			optionsMatches(secondaryOptions, 'ignoreSelectors', selector);
 
-		/**
-		 * Calculate the specificity of a simple selector (type, attribute, class, ID, or pseudos's own value).
-		 *
-		 * @param {import('postcss-selector-parser').Node} node
-		 * @returns {Specificity}
-		 */
-		const simpleSpecificity = (node) => {
-			if (isSelectorIgnored(node.toString())) {
-				return zeroSpecificity();
-			}
-
-			return selectorSpecificity(node);
-		};
-
-		/**
-		 * Calculate the specificity of the most specific direct child.
-		 *
-		 * @param {import('postcss-selector-parser').Container<string | undefined>} node
-		 * @returns {Specificity}
-		 */
-		const maxChildSpecificity = (node) =>
-			node.reduce((maxSpec, child) => {
-				const childSpecificity = nodeSpecificity(child); // eslint-disable-line no-use-before-define
-
-				return compare(childSpecificity, maxSpec) > 0 ? childSpecificity : maxSpec;
-			}, zeroSpecificity());
-
-		/**
-		 * If a `of <selector>` (`An+B of S`) is found in the specified pseudo node,
-		 * returns a copy of the pseudo node, ignoring a `of` selector (`An+B of S`).
-		 * Otherwise, returns the specified node as-is.
-		 *
-		 * @see https://drafts.csswg.org/selectors/#the-nth-child-pseudo
-		 * @param {import('postcss-selector-parser').Pseudo} pseudo
-		 * @returns {import('postcss-selector-parser').Pseudo}
-		 */
-		const ignoreOfSelectorIfAny = (pseudo) => {
-			/** @type {(node: import('postcss-selector-parser').Node | undefined) => boolean} */
-			const isOfSelector = (node) => node?.type === 'tag' && node.value === 'of';
-
-			/** @type {(node: import('postcss-selector-parser').Node | undefined) => boolean} */
-			const isSpace = (node) => node?.type === 'combinator' && node.value === ' ';
-
-			const nodes = pseudo.nodes[0]?.nodes ?? [];
-			const ofSelectorIndex = nodes.findIndex((child, i, children) => {
-				// Find ' of <selector>' nodes
-				return isSpace(child) && isOfSelector(children[i + 1]) && isSpace(children[i + 2]);
-			});
-
-			const ofSelector = nodes[ofSelectorIndex + 3];
-
-			if (!ofSelector || !ofSelector.value) return pseudo;
-
-			if (!isSelectorIgnored(ofSelector.value)) return pseudo;
-
-			const copy = pseudo.clone();
-			const rootSelector = copy.nodes[0];
-
-			if (rootSelector) {
-				// Remove ' of <selector>' nodes
-				rootSelector.nodes = rootSelector.nodes.slice(0, ofSelectorIndex);
-			}
-
-			return copy;
-		};
-
-		/**
-		 * Calculate the specificity of a pseudo selector including own value and children.
-		 *
-		 * @param {import('postcss-selector-parser').Pseudo} node
-		 * @returns {Specificity}
-		 */
-		const pseudoSpecificity = (node) => {
-			// `node.toString()` includes children which should be processed separately,
-			// so use `node.value` instead
-			const ownValue = node.value.toLowerCase();
-
-			if (ownValue === ':where') {
-				return zeroSpecificity();
-			}
-
-			let ownSpecificity;
-
-			if (isSelectorIgnored(ownValue)) {
-				ownSpecificity = zeroSpecificity();
-			} else if (aNPlusBOfSNotationPseudoClasses.has(ownValue.replace(/^:/, ''))) {
-				return selectorSpecificity(ignoreOfSelectorIfAny(node));
-			} else {
-				ownSpecificity = selectorSpecificity(node.clone({ nodes: [] }));
-			}
-
-			return specificitySum([ownSpecificity, maxChildSpecificity(node)]);
-		};
-
-		/**
-		 * @param {import('postcss-selector-parser').Node} node
-		 * @returns {boolean}
-		 */
-		const shouldSkipPseudoClassArgument = (node) => {
-			// postcss-selector-parser includes the arguments to nth-child() functions
-			// as "tags", so we need to ignore them ourselves.
-			// The fake-tag's "parent" is actually a selector node, whose parent
-			// should be the :nth-child pseudo node.
-			const parentNode = node.parent && node.parent.parent;
-
-			if (parentNode && parentNode.type === 'pseudo' && parentNode.value) {
-				const pseudoClass = parentNode.value.toLowerCase().replace(/^:/, '');
-
-				return (
-					aNPlusBNotationPseudoClasses.has(pseudoClass) || linguisticPseudoClasses.has(pseudoClass)
-				);
-			}
-
-			return false;
-		};
-
-		/**
-		 * Calculate the specificity of a node parsed by `postcss-selector-parser`.
-		 *
-		 * @param {import('postcss-selector-parser').Node} node
-		 * @returns {Specificity}
-		 */
-		const nodeSpecificity = (node) => {
-			if (shouldSkipPseudoClassArgument(node)) {
-				return zeroSpecificity();
-			}
-
-			switch (node.type) {
-				case 'attribute':
-				case 'class':
-				case 'id':
-				case 'tag':
-					return simpleSpecificity(node);
-				case 'pseudo':
-					return pseudoSpecificity(node);
-				case 'selector':
-					// Calculate the sum of all the direct children
-					return specificitySum(node.map((n) => nodeSpecificity(n)));
-				default:
-					return zeroSpecificity();
-			}
-		};
+		/** @type {import('@csstools/selector-specificity').CustomSpecificityCallback | undefined} */
+		const customSpecificity = secondaryOptions?.ignoreSelectors
+			? (node) => {
+					switch (node.type) {
+						case 'attribute':
+						case 'class':
+						case 'id':
+						case 'tag':
+							if (!isSelectorIgnored(node.toString())) {
+								return;
+							}
+
+							return zeroSpecificity();
+						case 'pseudo': {
+							if (!isSelectorIgnored(node.value.toLowerCase())) {
+								return;
+							}
+
+							if (!node.nodes?.length) {
+								return zeroSpecificity();
+							}
+
+							// We only ignore the current pseudo-class, not the specificity of the child nodes.
+							// Calculate the diff between specificity with and without child nodes.
+							const entireSpecificity = selectorSpecificity(node);
+
+							const emptySpecificity = selectorSpecificity(node.clone({ nodes: [] }));
+
+							return {
+								a: entireSpecificity.a - emptySpecificity.a,
+								b: entireSpecificity.b - emptySpecificity.b,
+								c: entireSpecificity.c - emptySpecificity.c,
+							};
+						}
+						default:
+						// Other node types are not ignorable.
+					}
+			  }
+			: undefined;
 
 		const [a, b, c] = primary.split(',').map((s) => Number.parseFloat(s));
 
@@ -236,8 +110,10 @@ const rule = (primary, secondaryOptions) => {
 
 			flattenNestedSelectorsForRule(ruleNode, result).forEach(({ selector, resolvedSelectors }) => {
 				resolvedSelectors.forEach((resolvedSelector) => {
+					const specificity = selectorSpecificity(resolvedSelector, { customSpecificity });
+
 					// Check if the selector specificity exceeds the allowed maximum
-					if (compare(nodeSpecificity(resolvedSelector), maxSpecificity) > 0) {
+					if (compare(specificity, maxSpecificity) > 0) {
 						const index = selector.first?.sourceIndex ?? 0;
 						const selectorStr = selector.toString().trim();
 
diff --git a/package-lock.json b/package-lock.json
index 76b512ca38..f3b4a86f09 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,7 +12,7 @@
         "@csstools/css-parser-algorithms": "^2.6.3",
         "@csstools/css-tokenizer": "^2.3.1",
         "@csstools/media-query-list-parser": "^2.1.11",
-        "@csstools/selector-specificity": "^3.0.3",
+        "@csstools/selector-specificity": "^3.1.0",
         "@dual-bundle/import-meta-resolve": "^4.1.0",
         "balanced-match": "^2.0.0",
         "colord": "^2.9.3",
@@ -1186,9 +1186,9 @@
       }
     },
     "node_modules/@csstools/selector-specificity": {
-      "version": "3.0.3",
-      "resolved": "https://registry.npmjs.org/@csstools/selector-specificity/-/selector-specificity-3.0.3.tgz",
-      "integrity": "sha512-KEPNw4+WW5AVEIyzC80rTbWEUatTW2lXpN8+8ILC8PiPeWPjwUzrPZDIOZ2wwqDmeqOYTdSGyL3+vE5GC3FB3Q==",
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/@csstools/selector-specificity/-/selector-specificity-3.1.0.tgz",
+      "integrity": "sha512-tGDFEHZ4XJeIt5NF7/nAfLGqPckmDZSnYne5gl67p4agQolE5s4rofdQ3e+VkeukfR91lVtSQ/Jt9DqM1ICiIQ==",
       "funding": [
         {
           "type": "github",
diff --git a/package.json b/package.json
index 9b66c10ffd..f054c0cd21 100644
--- a/package.json
+++ b/package.json
@@ -154,7 +154,7 @@
     "@csstools/css-parser-algorithms": "^2.6.3",
     "@csstools/css-tokenizer": "^2.3.1",
     "@csstools/media-query-list-parser": "^2.1.11",
-    "@csstools/selector-specificity": "^3.0.3",
+    "@csstools/selector-specificity": "^3.1.0",
     "@dual-bundle/import-meta-resolve": "^4.1.0",
     "balanced-match": "^2.0.0",
     "colord": "^2.9.3",