Firefox 149 ships adblock-rust, Brave’s MPL-2.0 Rust ad-blocking engine, disabled by default with no UI or filter lists included.
Key Takeaways
adblock-rust handles network request blocking, cosmetic filtering, and uses uBlock Origin-compatible filter list syntax.
The change landed via Bugzilla Bug 2013888, filed by Mozilla engineer Benjamin VanderSloot, titled “Add a prototype rich content blocking engine.”
Enabled via about:config flag privacy.trackingprotection.content.protection.enabled; filter lists must be manually added as URLs.
Waterfox, the Firefox fork, has already shipped adblock-rust in production, building directly on Mozilla’s implementation.
Brave VP of Privacy Shivan Kaul Sahib surfaced the change; it did not appear in Firefox 149 release notes.
Hacker News Comment Review
A Mozilla engineer clarified this is an experiment for improving Enhanced Tracking Protection, not a replacement for MV2 extension support or uBlock Origin; Firefox has no plans to drop MV2 add-ons.
The dominant concern is whether native ad-blocking becomes a pretext to deprecate MV2 extensions and shift toward acceptable-ads arrangements, mirroring Chrome’s Manifest V3 trajectory.
iOS users flagged a concrete gap: Firefox still cannot match Brave’s native content blocking on iOS, and this engine does not yet close that.
Notable Comments
@devsda: fears this is groundwork to phase out MV2 ad-block add-ons behind a “native availability” justification.
@MrAlex94: Waterfox developer; stumbled on the adblock-rs Gecko bindings via searchfox, confirming the integration timeline overlapped with his own independent adoption.
