Firefox for iOS has started cutting ads itself: what gets cut and why this isn’t uBlock Origin

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Firefox for iOS blocks ads on its own
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Mozilla published a help article Block ads in Firefox for iOS — about the built-in ad blocker in the mobile Firefox, without installing a separate filter app. The article itself states explicitly: the feature is experimental and being rolled out gradually, so some users don’t have the toggle yet. In the Firefox for iOS 153.0 release notes (July 21, 2026), the blocker is not mentioned at all — it’s enabled by a server flag, not by releasing a new build. The August 16 rollout was independently confirmed by AppleInsider.

Out of the box, the blocker is disabled. It can be enabled in two ways: Settings → Browsing → Content → Ad Blocker or on the fly from the menu of a specific site.

Info:

What Mozilla promises to block: third-party ad networks and exchanges, advertising trackers, “many third-party ads shown by the site,” as well as intrusive formats — pop-ups and overlays.

What will stay in place: ads in search results and sponsored blocks on the Firefox home page and new tab. The wording about “many” isn’t accidental — Mozilla notes separately that some ads will still slip through because sites use different advertising technologies.

Why this is principled not to be compared to uBlock Origin

This is where one should pause, because people often have inflated expectations. On iOS, any browser from the App Store renders pages with the WebKit engine, and content filtering inside the app is declarative: the browser compiles a JSON list of rules of the form “trigger → action” and passes it to the system for compilation. There are exactly four classes of actions — block a request, strip cookies, hide an element via css-display-none, cancel previous rules.

What this means in practice:

  • you don’t have access to every request at runtime — so there is no log of “who was calling where,” no body filtering, and no scriptlets with which uBlock Origin fixes anti-adblock stubs;
  • cosmetics are limited to CSS selectors; procedural constructs like :has-text() are not supported by the platform;
  • the compiled list has a hard ceiling on the number of rules.
Warning:

About the ceiling: based on the WebCore source in the BlockEmAll project, the system refuses to compile the list if the array length exceeds maxRuleCount — 50,000 or 150,000 entries depending on the version. Apple does not publicly name this limit in official docs, so the number should be considered a result of reverse engineering, not an official specification. But the fact of the ceiling matters: a full set of EasyList + EasyPrivacy filters reaches it, and any iOS blocker has to decide what to drop.

For comparison: on desktop, filtering runs into completely different limits — there was a discussion in the topic Manifest V2 is going away: five myths around uBlock Origin.

From here, reasonable expectations follow. The built-in Firefox blocker is at the level of “noticeably cleaner,” not “the page looks the same as in desktop Firefox with uBO.”

Who this changes the landscape for

If you already use a third-party content blocker for Safari (AdGuard, Wipr, 1Blocker), it does not apply to Firefox: those apps extend only Safari. The toggle in Firefox is a separate, independent entity, and you must enable it manually even for those who think “everything on the phone is already blocked.”

Success:

A quick check that the feature has reached you:

  1. Update Firefox from the App Store and restart the app.
  2. Settings → Browsing, section Content — look for the item Ad Blocker.
  3. If the item is not there — the flag has not rolled out to your profile yet; you cannot speed this up from the interface.
  4. If the item is present — enable it and test on any heavy-news site, comparing with the same page in Safari.

Separately, note that Firefox Focus from the same Mozilla has had blocking for many years and also acts as a system content blocker for Safari. So the news here is not “ad blocking appeared on iOS,” but “it no longer requires a separate app in the main Firefox browser.”

Sources

Question:

Who has the toggle already — how does it feel compared with AdGuard in Safari? And separately: has anyone encountered on iOS a site detecting the blocker and demanding its disablement, or do declarative blocking anti-ads simply not trigger?