Error 'MutationEvent is not defined' in Chrome and Edge — How to Fix (Updated 2025)
If you encountered an error message like: Uncaught ReferenceError: MutationEvent is not defined or an unexpected error window related to MutationEvent when opening a page or system, then this article is for you. 📅 Updated: May 2025 This issue affects regular users, not just developers accessing old systems or web apps that still rely on outdated technology. The error started to appear more frequently in Google Chrome and Microsoft Edge from mid-2024 onwards. In this article, I explain: ...