Mozilla says its WebExtensions API (Manifest) v3 updates in Firefox won't follow Google's implementation that hindered ad blockers
Like Brave, Opera, and Vivaldi, Mozilla distances itself from Google's planned extensions update that is anticipated to hinder ad blockers in Chrome.
Context & Ripple Effects
Google set the stage in May when it said Chrome's current ad-blocking capabilities would be restricted to enterprise users under its planned extensions overhaul, despite negative feedback (restricting Chrome ad blocking to enterprise). Mozilla's announcement is the first explicit refusal by a major non-Chromium vendor to copy that implementation into Firefox's version of the WebExtensions API.
The stakes come from the shared standard: WebExtensions was meant to let one codebase run across browsers, so Google's Manifest v3 choices were on track to become de facto rules for everyone. With Brave, Opera, and Vivaldi also distancing themselves, and the EFF later arguing the rules hurt innovation without stopping malware (EFF's critique of Manifest V3), this is the moment the 'one extensions platform' assumption starts to crack.
First-order effects
- Ad blocker developers can keep building full-strength blockers for Firefox using the APIs Google plans to restrict, making Firefox the default target for extensions whose Chrome versions will be degraded.
Second-order effects
- Extension developers now face maintaining divergent codebases — one for Google's Manifest v3 and one for Mozilla's — raising costs and pushing smaller blockers toward whichever browser offers the larger capable audience.
Third-order effects
- If the split holds, the WebExtensions standard effectively forks into a Google-controlled Chromium variant and a Mozilla variant, turning extension API governance into a competitive differentiator rather than a shared baseline — a divergence later visible in how widely ad-blocker capabilities differ across browsers (growing ad blocker disparities) and in non-Google browsers' joint refusal to adopt FLoC.
The trend: Browser vendors are splitting from Google's ad-driven platform decisions — Manifest v3 here, FLoC elsewhere — with privacy-preserving extension support becoming the main axis of differentiation for Firefox, Brave, Opera, and Vivaldi.