Errors / Blocked by the browser

[Deprecation] Listener added for a synchronous 'DOMNodeInserted' DOM Mutation Event.

A script watches the page with an old feature Chrome has removed.

Whatever reacted to changes on the page (a counter, an auto-resize, a lazy loader) silently stops.

Why it happens

• DOMNodeInserted, DOMSubtreeModified and the other mutation events were removed from Chrome in 2024; the listeners are added and never called.
• Often from old jQuery plugins, old editors, or old versions of a theme's scripts.

How to fix it

1. Replace them with a MutationObserver.
2. Update the plugin or library that adds them; the console line names its file.
3. Nothing throws when the listener is never called, so the symptom is a feature that silently stopped: a counter that no longer updates, an editor toolbar that does not react, a lazy loader that never fires. Search the site's scripts for DOMNodeInserted and DOMSubtreeModified to find every place, not only the one the console named.

Whose problem it is

Either the site's own code or a third party's, depending on where it comes from.

Often seen with

• Permissions policy violation: unloadA script used an old way to run code when the visitor leaves, which Chrome is phasing out.