Mutation Observer

Definitions

1. A browser API that watches for changes to the DOM tree — added/removed nodes, attribute changes, and text content modifications. Replaced the deprecated Mutation Events which caused severe performance issues. Used by frameworks, browser extensions, and accessibility tools to react to dynamic DOM changes.

   In plain English: A browser feature that notifies your code whenever something changes in the page's HTML structure.

   Example: "Use MutationObserver to detect when the third-party widget injects its iframe — then apply our custom styles to it."

Related Terms

• Consume
• Contract
• DOM
• Inspector
• Intersection Observer
• Resize Observer
• Portal
• Render Tree
• Window