Mozilla has shipped a built-in ad blocker for Firefox on iOS, using Apple's WebKit Content Blocker API and the EasyList filter list to strip third-party ads and trackers before they load. It's off by default, requires no extension install, and lives in Settings > Browsing > Ad Blocker. The move addresses a real gap: iOS doesn't support browser extensions the way desktop and Android do, so Mozilla built the capability into the browser itself. The carve-outs matter as much as the feature. Ads served directly by the site you're visiting — first-party ads — still appear. Search result ads still appear. And critically, Firefox's own sponsored shortcuts and sponsored content in new tabs are explicitly exempt. Mozilla's revenue depends heavily on search deals and sponsored placements, so the blocker is designed to protect that income stream while targeting the third-party ad ecosystem. This is Apple's WebKit Content Blocker technology under the hood, the same system Safari's content blockers use. Mozilla didn't build a novel blocking engine — it couldn't, because Apple requires all iOS browsers to use WebKit. The EasyList dependency means blocking quality is tied to a community-maintained filter list that Mozilla doesn't control. If EasyList misses something, Firefox's blocker misses it too. Mozilla frames the feature as user choice, and structurally it is: opt-in, transparent about what it does and doesn't block, with a feedback channel through Mozilla Connect. The messaging carefully balances user empowerment against the acknowledgment that advertising funds the open web. This is Mozilla threading a needle between its mission as a privacy-first organization and its financial reality as a company that makes most of its money from ad-adjacent deals. On desktop and Android, Firefox already supports uBlock Origin and other powerful extensions that block far more aggressively than this built-in tool. The iOS version is necessarily weaker — Apple's Content Blocker API imposes limits on rule counts and blocking granularity. Users switching from desktop Firefox with full extension support should calibrate expectations accordingly. The competitive signal is worth noting. Safari has offered content blocker support since iOS 9. Brave has shipped aggressive built-in blocking on iOS for years. Firefox arriving here in 2025 is catching up, not leading. But Mozilla's approach — opt-in, EasyList-based, with explicit carve-outs for its own monetization — is more conservative than Brave's and more transparent about its trade-offs than most. The deeper tension is structural: Mozilla needs advertising revenue to survive, but its user base expects it to fight advertising infrastructure. Every feature like this forces Mozilla to publicly draw the line between ads-that-fund-us and ads-that-bother-you. The exemption for sponsored new-tab content makes that line visible.
