Mozilla adds native ad blocking to Firefox for iOS
The browser now integrates Apple's WebKit Content Blockers to filter third-party ads, though Mozilla's own sponsored content remains.
Mozilla has begun a gradual, staged server-side rollout of a built-in ad blocker for Firefox on iOS. The move brings the mobile browser closer to feature parity with other platforms by providing native protection against third-party ads and trackers.
The new feature is off by default and must be manually enabled by users via Settings > Browsing > Ad Blocker. Because the rollout is handled server-side, the feature becomes available to users in stages as the toggle reaches individual devices. While the blocker targets most third-party advertisements, it specifically excludes ads on search result pages—such as those from Google, Bing, and DuckDuckGo—as well as sponsored content on Firefox's own Home and New Tab pages.
The WebKit Constraint
The implementation is a direct response to the technical limitations imposed by Apple. All browsers on iOS are required to use the WebKit rendering engine, and Apple restricts the use of traditional JavaScript-based ad-blocking extensions to preserve device performance and battery life. To bypass these restrictions, Mozilla had to build the functionality directly into the browser app.
According to The Register, the tool utilizes Apple's WebKit Content Blockers API, which employs a declarative bytecode format rather than JavaScript. To power the actual blocking rules, Mozilla uses a filter list based on EasyList, which has been converted into a JSON file for the system to process efficiently.
Privacy vs. Revenue
This rollout highlights a persistent tension between user privacy and Mozilla's business model. By blocking third-party ads while continuing to serve its own sponsored content, Mozilla maintains a revenue stream while offering a cleaner browsing experience for its users. This selective blocking approach ensures that the browser remains viable as a business while still addressing the primary pain points of the iOS browsing experience.
What to Watch
As the server-side rollout continues, users should check their settings to see if the toggle has become available on their devices. While the current focus is strictly on the iOS ecosystem due to the unique constraints of the App Store and WebKit, the industry will be watching to see if Mozilla introduces similar native integrations on other platforms or maintains its reliance on the existing extension ecosystem for desktop and Android users.