diff --git a/client/src/entrypoints/admin/core.js b/client/src/entrypoints/admin/core.js
index 2e4c6ef03a..22733fbc0d 100644
--- a/client/src/entrypoints/admin/core.js
+++ b/client/src/entrypoints/admin/core.js
@@ -3,11 +3,13 @@ import * as StimulusModule from '@hotwired/stimulus';
 
 import { Icon, Portal } from '../..';
 import { coreControllerDefinitions } from '../../controllers';
-import { escapeHtml } from '../../utils/text';
 import { InlinePanel } from '../../components/InlinePanel';
 import { MultipleChooserPanel } from '../../components/MultipleChooserPanel';
 import { initStimulus } from '../../includes/initStimulus';
 
+import { urlify } from '../../utils/urlify';
+import { escapeHtml } from '../../utils/text';
+
 /** Expose a global to allow for customisations and packages to build with Stimulus. */
 window.StimulusModule = StimulusModule;
 
@@ -38,6 +40,21 @@ window.InlinePanel = InlinePanel;
 
 window.MultipleChooserPanel = MultipleChooserPanel;
 
+/**
+ * Support legacy global URLify which can be called with `allowUnicode` as a third param.
+ * Was not documented and only used in modeladmin prepopulate JS.
+ *
+ * @deprecated RemovedInWagtail70
+ * @see https://github.com/django/django/blob/main/django/contrib/admin/static/admin/js/urlify.js#L156
+ *
+ * @param {string} str
+ * @param {number} numChars
+ * @param {boolean} allowUnicode
+ * @returns {string}
+ */
+window.URLify = (str, numChars = 255, allowUnicode = false) =>
+  urlify(str, { numChars, allowUnicode });
+
 $(() => {
   /* Dropzones */
   $('.drop-zone')
diff --git a/docs/releases/6.1.md b/docs/releases/6.1.md
index 3e86f63cae..e7e34cb889 100644
--- a/docs/releases/6.1.md
+++ b/docs/releases/6.1.md
@@ -281,3 +281,38 @@ In the new approach, we no longer need to attach an inline script but instead us
 ### Removal of jQuery from base client-side Widget and BoundWidget classes
 
 The JavaScript base classes `Widget` and `BoundWidget` that provide client-side access to form widgets (see [](streamfield_widget_api)) no longer use jQuery. The `element` argument passed to the `BoundWidget` constructor, and the `input` property of `BoundWidget`, are now native DOM elements rather than jQuery collections. User code that extends these classes should be updated accordingly.
+
+### `window.URLify` deprecated
+
+The undocumented client-side global util `window.URLify` is now deprecated and will be removed in a future release.
+
+If this was required for slug field behavior, it's recommended that the `SlugInput` widget be used instead. This will automatically convert values entered into a suitable slug in the browser while respecting the global configuration `WAGTAIL_ALLOW_UNICODE_SLUGS`.
+
+```python
+from wagtail.admin.widgets.slug import SlugInput
+# ... other imports
+
+class MyPage(Page):
+    promote_panels = [
+        FieldPanel("slug", widget=SlugInput),
+        # ... other panels
+    ]
+```
+
+If you require this for custom JavaScript functionality, it's recommended you either include your own implementation from the original [Django URLify source](https://raw.githubusercontent.com/wagtail/wagtail/stable/6.0.x/wagtail/admin/static_src/wagtailadmin/js/vendor/urlify.js). Alternatively, the [`slugify`](https://www.npmjs.com/package/slugify) or [`parameterize` (a Django URLify port)](https://www.npmjs.com/package/parameterize) NPM packages might be suitable.
+
+### `window.XRegExp` polyfill removed
+
+The legacy `window.XRegExp` global polyfill util has been removed and will throw an error if called.
+
+Instead, any usage of this should be updated to the well supported [browser native Regex implementation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_expressions).
+
+```javascript
+// old
+const newStr = XRegExp.replace(originalStr, XRegExp('[ab+c]', 'g'), '')
+
+// new (with RegExp)
+const newStr = originalStr.replace(new RegExp('[ab+c]', 'g'), '')
+// OR
+const newStr = originalStr.replace(/[ab+c]/g, 'g'), '')
+```