diff --git a/edit/linter-manager.js b/edit/linter-manager.js
index ad262933..1beba210 100644
--- a/edit/linter-manager.js
+++ b/edit/linter-manager.js
@@ -133,6 +133,7 @@ linterMan.DEFAULTS = {
     'errors': 1,
     'globals-in-document': 1,
     'known-properties': 1,
+    'known-pseudos': 1,
     'selector-newline': 1,
     'shorthand-overrides': 1,
     'simple-not': 1,
diff --git a/js/csslint/csslint.js b/js/csslint/csslint.js
index 80a36867..012e66d7 100644
--- a/js/csslint/csslint.js
+++ b/js/csslint/csslint.js
@@ -1144,6 +1144,228 @@ CSSLint.addRule['known-properties'] = [{
   });
 }];
 
+CSSLint.addRule['known-pseudos'] = [{
+  name: 'Require use of known pseudo selectors',
+  url: 'https://developer.mozilla.org/docs/Learn/CSS/Building_blocks/Selectors/Pseudo-classes_and_pseudo-elements',
+  browsers: 'All',
+}, (rule, parser, reporter) => {
+  // 1 = requires ":"
+  // 2 = requires "::"
+  const Func = 4; // must be :function()
+  const FuncToo = 8; // both :function() and :non-function
+  const WK = 0x10;
+  const Moz = 0x20;
+  const definitions = {
+    // elements
+    'after': 1 + 2, // also allows ":"
+    'backdrop': 2,
+    'before': 1 + 2, // also allows ":"
+    'cue': 2,
+    'cue-region': 2,
+    'file-selector-button': 2,
+    'first-letter': 1 + 2, // also allows ":"
+    'first-line': 1 + 2, // also allows ":"
+    'grammar-error': 2,
+    'highlight': 2 + Func,
+    'marker': 2,
+    'part': 2 + Func,
+    'placeholder': 2 + Moz,
+    'selection': 2 + Moz,
+    'slotted': 2 + Func,
+    'spelling-error': 2,
+    'target-text': 2,
+    // classes
+    'active': 1,
+    'any-link': 1 + Moz + WK,
+    'autofill': 1 + WK,
+    'blank': 1,
+    'checked': 1,
+    'current': 1 + FuncToo,
+    'default': 1,
+    'defined': 1,
+    'dir': 1 + Func,
+    'disabled': 1,
+    'drop': 1,
+    'empty': 1,
+    'enabled': 1,
+    'first': 1,
+    'first-child': 1,
+    'first-of-type': 1,
+    'focus': 1,
+    'focus-visible': 1,
+    'focus-within': 1,
+    'fullscreen': 1,
+    'future': 1,
+    'has': 1 + Func,
+    'host': 1 + FuncToo,
+    'host-context': 1 + Func,
+    'hover': 1,
+    'in-range': 1,
+    'indeterminate': 1,
+    'invalid': 1,
+    'is': 1 + Func,
+    'lang': 1 + Func,
+    'last-child': 1,
+    'last-of-type': 1,
+    'left': 1,
+    'link': 1,
+    'local-link': 1,
+    'not': 1 + Func,
+    'nth-child': 1 + Func,
+    'nth-col': 1 + Func,
+    'nth-last-child': 1 + Func,
+    'nth-last-col': 1 + Func,
+    'nth-last-of-type': 1 + Func,
+    'nth-of-type': 1 + Func,
+    'only-child': 1,
+    'only-of-type': 1,
+    'optional': 1,
+    'out-of-range': 1,
+    'past': 1,
+    'paused': 1,
+    'picture-in-picture': 1,
+    'placeholder-shown': 1,
+    'playing': 1,
+    'read-only': 1,
+    'read-write': 1,
+    'required': 1,
+    'right': 1,
+    'root': 1,
+    'scope': 1,
+    'state': 1 + Func,
+    'target': 1,
+    'target-within': 1,
+    'user-invalid': 1,
+    'valid': 1,
+    'visited': 1,
+    'where': 1 + Func,
+    'xr-overlay': 1,
+    // ::-webkit-scrollbar specific classes
+    'corner-present': 1,
+    'decrement': 1,
+    'double-button': 1,
+    'end': 1,
+    'horizontal': 1,
+    'increment': 1,
+    'no-button': 1,
+    'single-button': 1,
+    'start': 1,
+    'vertical': 1,
+    'window-inactive': 1 + Moz,
+  };
+  const definitionsPrefixed = {
+    'any': 1 + Func + Moz + WK,
+    'calendar-picker-indicator': 2 + WK,
+    'clear-button': 2 + WK,
+    'color-swatch': 2 + WK,
+    'color-swatch-wrapper': 2 + WK,
+    'date-and-time-value': 2 + WK,
+    'datetime-edit': 2 + WK,
+    'datetime-edit-ampm-field': 2 + WK,
+    'datetime-edit-day-field': 2 + WK,
+    'datetime-edit-fields-wrapper': 2 + WK,
+    'datetime-edit-hour-field': 2 + WK,
+    'datetime-edit-millisecond-field': 2 + WK,
+    'datetime-edit-minute-field': 2 + WK,
+    'datetime-edit-month-field': 2 + WK,
+    'datetime-edit-second-field': 2 + WK,
+    'datetime-edit-text': 2 + WK,
+    'datetime-edit-week-field': 2 + WK,
+    'datetime-edit-year-field': 2 + WK,
+    'drag': 1 + WK,
+    'drag-over': 1 + Moz,
+    'file-upload-button': 2 + WK,
+    'focus-inner': 2 + Moz,
+    'focusring': 1 + Moz,
+    'full-page-media': 1 + WK,
+    'full-screen': 1 + Moz + WK,
+    'full-screen-ancestor': 1 + Moz + WK,
+    'inner-spin-button': 2 + WK,
+    'input-placeholder': 1 + 2 + WK + Moz,
+    'loading': 1 + Moz,
+    'media-controls': 2 + WK,
+    'media-controls-current-time-display': 2 + WK,
+    'media-controls-enclosure': 2 + WK,
+    'media-controls-fullscreen-button': 2 + WK,
+    'media-controls-mute-button': 2 + WK,
+    'media-controls-overlay-enclosure': 2 + WK,
+    'media-controls-overlay-play-button': 2 + WK,
+    'media-controls-panel': 2 + WK,
+    'media-controls-play-button': 2 + WK,
+    'media-controls-time-remaining-display': 2 + WK,
+    'media-controls-timeline': 2 + WK,
+    'media-controls-timeline-container': 2 + WK,
+    'media-controls-toggle-closed-captions-button': 2 + WK,
+    'media-controls-volume-slider': 2 + WK,
+    'media-slider-container': 2 + WK,
+    'media-slider-thumb': 2 + WK,
+    'media-text-track-container': 2 + WK,
+    'media-text-track-display': 2 + WK,
+    'media-text-track-region': 2 + WK,
+    'media-text-track-region-container': 2 + WK,
+    'meter-bar': 2 + WK,
+    'meter-even-less-good-value': 2 + WK,
+    'meter-inner-element': 2 + WK,
+    'meter-optimum-value': 2 + WK,
+    'meter-suboptimum-value': 2 + WK,
+    'progress-bar': 2 + WK,
+    'progress-inner-element': 2 + WK,
+    'progress-value': 2 + WK,
+    'resizer': 2 + WK,
+    'scrollbar': 2 + WK,
+    'scrollbar-button': 2 + WK,
+    'scrollbar-corner': 2 + WK,
+    'scrollbar-thumb': 2 + WK,
+    'scrollbar-track': 2 + WK,
+    'scrollbar-track-piece': 2 + WK,
+    'search-cancel-button': 2 + WK,
+    'slider-container': 2 + WK,
+    'slider-runnable-track': 2 + WK,
+    'slider-thumb': 2 + WK,
+    'textfield-decoration-container': 2 + WK,
+  };
+  const rx = /^(:+)(?:-(\w+)-)?([^(]+)(\()?/i;
+  const allowsFunc = Func + FuncToo;
+  const allowsPrefix = WK + Moz;
+  const {lower} = parserlib.util;
+  const checkSelector = ({parts}) => {
+    for (const {modifiers} of parts || []) {
+      if (!modifiers) continue;
+      for (const mod of modifiers) {
+        if (mod.type === 'pseudo') {
+          const {text} = mod;
+          const [all, colons, prefix, name, paren] = rx.exec(lower(text)) || 0;
+          const defPrefixed = definitionsPrefixed[name];
+          const def = definitions[name] || defPrefixed;
+          for (const err of !def ? ['Unknown pseudo'] : [
+            colons.length > 1
+              ? !(def & 2) && 'Must use : in'
+              : !(def & 1) && all !== ':-moz-placeholder' && 'Must use :: in',
+            paren
+              ? !(def & allowsFunc) && 'Unexpected ( in'
+              : (def & Func) && 'Must use ( after',
+            prefix ?
+              (
+                !(def & allowsPrefix) ||
+                prefix === 'webkit' && !(def & WK) ||
+                prefix === 'moz' && !(def & Moz)
+              ) && 'Unexpected prefix in'
+              : defPrefixed && `Must use ${
+                (def & WK) && (def & Moz) && '-webkit- or -moz-' ||
+                (def & WK) && '-webkit-' || '-moz-'} prefix in`,
+          ]) {
+            if (err) reporter.report(`${err} ${text.slice(0, all.length)}`, mod, rule);
+          }
+        } else if (mod.args) {
+          mod.args.forEach(checkSelector);
+        }
+      }
+    }
+  };
+  parser.addListener('startrule', e => e.selectors.forEach(checkSelector));
+  parser.addListener('supportsSelector', e => checkSelector(e.selector));
+}];
+
 CSSLint.addRule['order-alphabetical'] = [{
   name: 'Alphabetical order',
   desc: 'Assure properties are in alphabetical order',
diff --git a/js/csslint/parserlib.js b/js/csslint/parserlib.js
index fe43aa79..a1c40df0 100644
--- a/js/csslint/parserlib.js
+++ b/js/csslint/parserlib.js
@@ -3582,7 +3582,8 @@ self.parserlib = (() => {
         }
       } else if (stream.match(Tokens.FUNCTION, ['selector('])) {
         this._ws();
-        this._selector();
+        const selector = this._selector();
+        this.fire({type: 'supportsSelector', selector}, selector);
         stream.mustMatch(Tokens.RPAREN);
       } else {
         this._supportsDecl();
@@ -4671,6 +4672,9 @@ self.parserlib = (() => {
       SyntaxError,
       SyntaxUnit,
       TokenStreamBase,
+      fastJoin,
+      isPseudoElement,
+      lower,
       rxVendorPrefix,
       describeProp: vtExplode,
     },