diff --git a/modules/core/LocalizationSystem.js b/modules/core/LocalizationSystem.js
index 563b981e8..28333d57c 100644
--- a/modules/core/LocalizationSystem.js
+++ b/modules/core/LocalizationSystem.js
@@ -208,8 +208,8 @@ export class LocalizationSystem extends AbstractSystem {
     //   4. English (always fallback)
     const requestedLocales = (this._preferredLocaleCodes || [])
       .concat(urlLocaleCodes)
-      .concat(utilDetect().browserLocales)   // Locales preferred by the browser in priority order.
-      .concat(['en']);                       // Fallback to English since it's the only guaranteed complete language
+      .concat(utilDetect().locales)   // Locales preferred by the browser in priority order.
+      .concat(['en']);                // Fallback to English since it's the only guaranteed complete language
 
     this._currLocaleCodes = this._getSupportedLocales(requestedLocales);
     this._currLocaleCode = this._currLocaleCodes[0];   // First is highest priority locale; the rest are fallbacks
diff --git a/modules/util/detect.js b/modules/util/detect.js
index e4851a35b..6f4479816 100644
--- a/modules/util/detect.js
+++ b/modules/util/detect.js
@@ -1,9 +1,26 @@
 
-let _detected;
-
+let _cached;
+
+/**
+ * `utilDetect` detects things from the user's browser.
+ * It returns an object with the following:
+ * {
+ *   support: true,                   // Is Rapid supported?  (basically - not Internet Explorer)
+ *   browser: "Chrome",               // e.g. 'Edge','msie','Opera','Chrome','Safari','Firefox'
+ *   version: "133.0",                // reported browser version
+ *   languages: ['en-US'],            // Array sourced from `navigator.languages`
+ *   host: "http://127.0.0.1:8080/",
+ *   os: "mac",
+ *   platform: "Macintosh",
+ *   prefersColorScheme: 'light',         // 'light' or 'dark'
+ *   prefersContrast: null,               // 'more', 'less', or `null`
+ *   prefersReducedMotion: false,         // `true` or `false`
+ *   prefersReducedTransparency: false    // `true` or `false`
+ * }
+ */
 export function utilDetect(refresh) {
-  if (_detected && !refresh) return _detected;
-  _detected = {};
+  if (_cached && !refresh) return _cached;
+  _cached = {};
 
   const ua = navigator.userAgent;
   let m = null;
@@ -11,84 +28,63 @@ export function utilDetect(refresh) {
   /* Browser */
   m = ua.match(/(edg)\/?\s*(\.?\d+(\.\d+)*)/i);   // Edge
   if (m !== null) {
-    _detected.browser = 'Edge';
-    _detected.version = m[2];
+    _cached.browser = 'Edge';
+    _cached.version = m[2];
   }
-  if (!_detected.browser) {
+  if (!_cached.browser) {
     m = ua.match(/Trident\/.*rv:([0-9]{1,}[\.0-9]{0,})/i);   // IE11
     if (m !== null) {
-      _detected.browser = 'msie';
-      _detected.version = m[1];
+      _cached.browser = 'msie';
+      _cached.version = m[1];
     }
   }
-  if (!_detected.browser) {
+  if (!_cached.browser) {
     m = ua.match(/(opr)\/?\s*(\.?\d+(\.\d+)*)/i);   // Opera 15+
     if (m !== null) {
-      _detected.browser = 'Opera';
-      _detected.version = m[2];
+      _cached.browser = 'Opera';
+      _cached.version = m[2];
     }
   }
-  if (!_detected.browser) {
+  if (!_cached.browser) {
     m = ua.match(/(opera|chrome|safari|firefox|msie)\/?\s*(\.?\d+(\.\d+)*)/i);
     if (m !== null) {
-      _detected.browser = m[1];
-      _detected.version = m[2];
+      _cached.browser = m[1];
+      _cached.version = m[2];
       m = ua.match(/version\/([\.\d]+)/i);
-      if (m !== null) _detected.version = m[1];
+      if (m !== null) _cached.version = m[1];
     }
   }
-  if (!_detected.browser) {
-    _detected.browser = navigator.appName;
-    _detected.version = navigator.appVersion;
+  if (!_cached.browser) {
+    _cached.browser = navigator.appName;
+    _cached.version = navigator.appVersion;
   }
 
-  // keep major.minor version only..
-  _detected.version = _detected.version.split(/\W/).slice(0,2).join('.');
-
-  // detect other browser capabilities
-  // Legacy Opera has incomplete svg style support. See #715
-  _detected.opera = (_detected.browser.toLowerCase() === 'opera' && parseFloat(_detected.version) < 15 );
+  // Keep major.minor version only..
+  _cached.version = _cached.version.split(/\W/).slice(0,2).join('.');
 
-  if (_detected.browser.toLowerCase() === 'msie') {
-    _detected.support = false;
+  if (_cached.browser.toLowerCase() === 'msie') {
+    _cached.support = false;
   } else {
-    _detected.support = true;
+    _cached.support = true;
   }
 
-  _detected.filedrop = (window.FileReader && 'ondrop' in window);
-  _detected.download = !(_detected.ie || _detected.browser.toLowerCase() === 'edge');
-  _detected.cssfilters = !(_detected.ie || _detected.browser.toLowerCase() === 'edge');
-
-
   /* Platform */
   if (/Win/.test(ua)) {
-    _detected.os = 'win';
-    _detected.platform = 'Windows';
+    _cached.os = 'win';
+    _cached.platform = 'Windows';
   } else if (/Mac/.test(ua)) {
-    _detected.os = 'mac';
-    _detected.platform = 'Macintosh';
+    _cached.os = 'mac';
+    _cached.platform = 'Macintosh';
   } else if (/X11/.test(ua) || /Linux/.test(ua)) {
-    _detected.os = 'linux';
-    _detected.platform = 'Linux';
+    _cached.os = 'linux';
+    _cached.platform = 'Linux';
   } else {
-    _detected.os = 'win';
-    _detected.platform = 'Unknown';
+    _cached.os = 'win';
+    _cached.platform = 'Unknown';
   }
 
-
   /* Locale */
-  // An array of locales requested by the browser in priority order.
-  _detected.browserLocales = Array.from(new Set( // remove duplicates
-      [navigator.language]
-        .concat(navigator.languages || [])
-        .concat([
-            // old property for backwards compatibility
-            navigator.userLanguage
-        ])
-        // remove any undefined values
-        .filter(Boolean)
-    ));
-
+  _cached.locales = navigator.languages.slice();  // shallow copy
 
   /* Host */
   const loc = window.top.location;
@@ -97,8 +93,13 @@ export function utilDetect(refresh) {
     origin = loc.protocol + '//' + loc.hostname + (loc.port ? ':' + loc.port: '');
   }
 
-  _detected.host = origin + loc.pathname;
+  _cached.host = origin + loc.pathname;
 
+  _cached.prefersColorScheme = window.matchMedia?.('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+  _cached.prefersContrast = window.matchMedia?.('(prefers-contrast: more)').matches ? 'more'
+    : window.matchMedia?.('(prefers-contrast: less)').matches ? 'less' : null;
+  _cached.prefersReducedMotion = window.matchMedia?.('(prefers-reduced-motion: reduce)').matches;
+  _cached.prefersReducedTransparency = window.matchMedia?.('(prefers-reduced-transparency: reduce)').matches;
 
-  return _detected;
+  return _cached;
 }
diff --git a/test/unit/util/detect.test.js b/test/unit/util/detect.test.js
index 5290c4fce..24f478aa3 100644
--- a/test/unit/util/detect.test.js
+++ b/test/unit/util/detect.test.js
@@ -1,4 +1,4 @@
-import { afterEach, beforeEach, describe, it } from 'node:test';
+import { before, after, beforeEach, describe, it } from 'node:test';
 import { strict as assert } from 'node:assert';
 import * as Rapid from '../../../modules/headless.js';
 
@@ -15,45 +15,45 @@ if (!global.window) {  // mock window for Node
 }
 
 describe('utilDetect', () => {
-  let navigator;
-  let originalNavigator = global.navigator;
+  let origNavigator;
+
+  before(() => {
+    origNavigator = global.navigator;
+  });
+
+  after(() => {
+    global.navigator = origNavigator;  // restore original
+  });
+
   beforeEach(() => {
-    // Create a mock navigator object with a languages and platform property
-    navigator = {
-      languages: ['en-US'],
-      platform: 'Windows'
+    const mock = {
+      languages: ['en-US', 'en'],
+      platform: 'MacIntel',
+      userAgent: 'Mozilla/5.0 (Macintosh; Intel Mac) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36'
     };
-    // Set the mock navigator object as the global navigator object
-    global.navigator = navigator;
-  });
-  afterEach(() => {
-    // Reset the global navigator object to its original value
-    global.navigator = originalNavigator;
+    // Copy the original navigator, so we can safely change things.
+    global.navigator = Object.assign(origNavigator || mock);
   });
 
   it('should detect the browser and version', () => {
     const ua = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3';
-    global.navigator = { userAgent: ua };
-    const detected = Rapid.utilDetect();
+    global.navigator.userAgent = ua;
+    const detected = Rapid.utilDetect(true);
     assert.strictEqual(detected.browser, 'Chrome');
     assert.strictEqual(detected.version, '58.0');
   });
 
-  it('should detect the platform', () => {
+  it('should detect the os and platform', () => {
     const ua = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3';
-    global.navigator = { userAgent: ua };
-    const detected = Rapid.utilDetect();
+    global.navigator.userAgent = ua;
+    const detected = Rapid.utilDetect(true);
     assert.strictEqual(detected.os, 'win');
     assert.strictEqual(detected.platform, 'Windows');
   });
 
   it('should detect the locale', () => {
-    const detected = Rapid.utilDetect();
-    assert.ok(!detected.browserLocales.includes('en-US'));
-  });
-
-  it('should detect the platform', () => {
-    const detected = Rapid.utilDetect();
-    assert.strictEqual(detected.platform, 'Windows');
+    global.navigator.languages = ['es'];
+    const detected = Rapid.utilDetect(true);
+    assert.ok(detected.locales.includes('es'));
   });
-});
\ No newline at end of file
+});