Firefox is now the last major browser where uBlock Origin runs
Edge began retiring Manifest V2 this month and Chrome's store deletes the leftovers on August 31. Mozilla says its support is not going anywhere.
Chrome dropped it, Edge is dropping it now. Exactly one major browser still commits to the ad blocker's API.
With Microsoft Edge now retiring Manifest V2 extensions for consumers, Firefox is the last major browser that still runs uBlock Origin, PCWorld reported this week. Mozilla's response, posted on Bluesky: our support for uBlock Origin is not going anywhere.
How the walls closed in
- Chrome disabled Manifest V2 across its stable channel starting with Chrome 138 in mid-2025.
- The Chrome Web Store removes all remaining Manifest V2 extensions on August 31, 2026.
- Microsoft said on August 7 that Edge begins retiring MV2 for consumers this month, finishing by the end of 2026, with enterprise deprecation starting in early 2027.
- Brave, built on Chromium, keeps MV2 extensions alive by hosting them itself.
The technical core of the fight has not changed: Manifest V3 replaces the blocking webRequest API with declarativeNetRequest, which caps rule counts and removes the dynamic, per-request filtering logic uBlock Origin is built on. The author has said for years that a full uBlock Origin cannot exist under MV3, which is why Chrome users get the reduced uBlock Origin Lite instead.
Mozilla is moving the other direction on mobile too: Firefox for iOS just shipped a native ad blocker, built into the browser where Apple's extension rules cannot reach it.
Why a build studio cares
The sites we build get measured by analytics and judged on that measurement, so blocker behavior is not a side issue for us. Ad blocking is not going away, it is redistributing: into Firefox, into Brave's self-hosted store, into network-level blockers and iOS content blockers. Blocker behavior now differs sharply per browser, and your analytics blind spots differ with it. A site that renders fine in Chrome with Lite rules can break differently under Firefox with full uBlock Origin.
Next step: add Firefox with uBlock Origin to your test matrix if it is not there, and compare your analytics numbers against server logs for one week. The gap is your blocked-measurement rate, and it just got more browser-dependent. If your analytics and your server logs disagree and you want to know why, write to us at hello@gattyworks.com.