In early?2025, Google began enforcing the transition from Manifest?V2 to Manifest?V3 in Chrome. This change disabled legacy extensions like the full version of uBlock Origin, which relied on powerful APIs no longer permitted under MV3. The popular extension was a mainstay on most browsers making surfing the web palatable–eliminating most ads from web pages.
With Chrome’s ad?blocking strength diminished, many users flocked to Firefox, which continues to support both Manifest?V2 and V3. Have you seen this shift in your analytics?
Mozilla’s official add?ons site reports over 9?million active uBlock Origin installs on Firefox, compared with around 29?million on Chromium
What This Means for Webmasters
Growing traffic from Firefox means ensuring websites load properly for the browser. Here are some design-specific considerations to keep in mind:
1. uBO Compatibility & CNAME Uncloaking
Pages should be tested under uBO to ensure essential elements (e.g., embedded videos, trackers) aren’t blocked unintentionally.
2. Privacy?First Defaults
Firefox emphasizes privacy with features like DNS?over?HTTPS, tracking protection, and default container policies . Design your site assuming third-party cookies and trackers may be disabled. Use standard APIs (e.g., Web Storage, IndexedDB, HTTP cookies) for essential functionality.
3. Performance under Ad?Block
Firefox’s tracking protection can enhance page load times—data shows up to a 44% median reduction in page load times with tracking blocked. Webmasters should continue to optimize images, defer non-critical scripts, and avoid dependencies on blocked ad or tracking domains.
5. Progressive Web App (PWA) Support
Firefox now supports key APIs like Service Workers and Web App Manifests on par with Chrome. Ensure your PWA is fully compatible by verifying installable experiences and offline functionality work seamlessly in Firefox.
Other considerations from Mozilla here.
Any others you might add?