Mozilla will retain ManifestV2 support in Firefox, so ad blockers will survive

Google is pushing developers to adopt Manifest V3, phasing out older extensions. While other browsers are discontinuing support for Manifest V2 entirely, Firefox maintains compatibility with both Manifest V2 and V3.

Google’s decision to prioritize Manifest V3 has a negative effect. It significantly restricts the API available to extensions. So those which modify the page content heavily, i.e. ad blockers, will stop working. They V3-compliant versions aren't so powerful.

Firefox aims to adopt nearly all features and specifications of the new manifest format, including the declarative API for content filtering (declarativeNetRequest). Unlike Chrome, however, it will retain support for the legacy blocking mode of the webRequest API until the new API fully addresses the needs of developers who rely on it. This approach ensures compatibility with Chrome extensions while preserving functionality for existing add-ons that depend on the webRequest API.

Besides Firefox, Brave and Opera are two other browsers that maintain compatibility with both Manifest V2 and its newer successor, Manifest V3.

Meanwhile, Microsoft Edge started disabling Manifest V2 add-ons. Similarly to Chrome, those include the popular uBlock Origin ad blocker. The browser advises to deactivate it due to its end of support.

Apparently, uBlock Origin will stop working in Microsoft Edge in the near future. As an alternative, users can consider uBlock Origin Lite (a project by the same developer), AdGuard blocker or any other add-on with Manifest V3 support.