Firefox for iOS rolls out built-in ad blocking, but Mozilla's own ads remain visible

Feature uses Apple's WebKit Content Blockers; Mozilla says no plans to expand native ad blocking beyond iOS

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By LineZotpaper

Published2 September 2026

Read Time2 min

Mozilla has begun rolling out a native ad-blocking feature to Firefox for iOS, ending weeks of anticipation by integrating Apple's WebKit Content Blockers into the browser. The feature, off by default, will block third-party ads and trackers but will not block ads on Mozilla's own pages, including the new tab page.

Mozilla officially moved the ad-blocking feature for iOS Firefox out of the experimental phase on Tuesday, according to The Register. The organization explained that bringing ad blocking to iOS required building it directly into the browser because Apple forces all iOS web browsers to use its WebKit rendering engine rather than their own back ends.

To implement the feature, Mozilla incorporated Apple's WebKit Content Blockers. Apple argues that traditional JavaScript-based content-blocking extensions have "significant performance drawbacks," such as high energy use, increased page load times, and memory consumption. WebKit Content Blockers instead use a structured, declarative format that executes in bytecode for each resource request, modifying requests or injecting CSS changes as pages load.

Mozilla said the implementation involves converting the EasyList filter — originally designed for the classic Adblock extension — into a JSON file for WebKit.

The ad blocker is off by default and is rolling out gradually. Users who have access can enable it by opening the in-app settings menu, tapping Browsing, and toggling the Ad Blocker field. The feature also requires Remote Improvements to be enabled, which lets Mozilla push fixes and changes between full releases. Notably, Mozilla decoupled Remote Improvements from browser telemetry in Firefox 148 in February, so users no longer have to allow telemetry collection to use the feature.

Once enabled, the blocker will handle ad-related trackers, third-party ads from advertising networks, third-party ads served by websites, and popups/overlays. It will not block ads on search result pages, sponsored content on Firefox's home or new tab page, or ads served directly by websites. Mozilla warned the feature may not work in all places, which it said is common for ad blockers.

When asked about potential expansion to desktop or Android, Mozilla told The Register it has no plans to bring built-in ad blocking outside iOS. "We value that ecosystem and will continue to support it," the organization said.

Analysis

Why This Matters

iOS Firefox users who rely on extensions for ad blocking now have a built-in option, reducing the need for workarounds on a platform where browser extensions are limited.
Mozilla's decision to keep its own ads visible while blocking others raises questions about conflicts of interest in ad-blocking tools.
The gradual rollout means not all users will see the feature immediately, and its effectiveness may vary across sites.

Background

Firefox has long supported ad-blocking and privacy extensions on desktop and Android, but iOS browsers are constrained by Apple's requirement that all web browsers use WebKit. This has historically limited the functionality of iOS browsers compared to their desktop counterparts. Mozilla's move to embed ad blocking directly into the browser is a workaround specific to iOS's architecture, relying on Apple's own content-blocking framework rather than traditional extensions.

Key Perspectives

Mozilla: The organization frames the feature as giving iOS users control over their web experience, but it also protects its own advertising revenue by exempting Mozilla's pages and sponsored content from blocking. It says it remains committed to supporting third-party ad-blocking extensions on other platforms. Apple: Apple's WebKit Content Blockers reflect the company's preference for performance and energy efficiency over the flexibility of JavaScript-based extensions. Apple positions this as protecting iOS users from resource-heavy ad blockers. Critics/Skeptics: Users may question why Mozilla's own ads are untouched, and ad-blocking enthusiasts may worry that built-in features could eventually undermine the extension ecosystem. The requirement to enable Remote Improvements could also raise privacy concerns despite the telemetry decoupling.

What to Watch

How quickly Mozilla expands the rollout to all iOS users and whether user feedback leads to adjustments.
Whether Mozilla revises its stated position on keeping built-in ad blocking iOS-only if adoption is strong.
Any sites that find ways to bypass the blocker, prompting Mozilla to update its filter rules.

Sources

Firefox helps iPhone users bypass ads on web sites while making money showing its own ads — www.theregister.com - Articles