Mozilla adds a built-in ad blocker to Firefox on iOS, built on Apple’s WebKit API

Mozilla has launched a built-in ad blocker for Firefox on iOS, built on Apple’s WebKit content blocker technology with the EasyList filter and switched off by default. Apple opened its browser engine to rivals in March 2024 to comply with the Digital Markets Act, and no alternative engine has shipped to a European iPhone since.

Firefox on iOS finally has a built-in ad blocker. It arrived with Firefox 155 after a few weeks of testing, Digital Trends reported.

It works on Apple’s terms rather than Mozilla’s. The feature uses Apple’s WebKit content blocker with the community-maintained EasyList filter, and it is switched off until you find it in settings.

What it cannot block is the more telling part. Ads served by the site itself remain, so do ads in search results, and Mozilla’s own sponsored shortcuts are handled separately.

Firefox is late to this by years. Brave, Opera and Vivaldi have all shipped built-in blocking on iOS already, and desktop users have had extensions for far longer.

The reason is the engine underneath. Every browser on an iPhone renders with WebKit, so Firefox on iOS is Apple’s engine wearing a different interface.

Europe changed that rule on paper. Apple opened BrowserEngineKit in March 2024 to comply with the Digital Markets Act. The interface arrived with iOS 17.4 and applies only in the European Union.

Two and a half years on, nobody has shipped one. Google and Mozilla have both prototyped their own engines and neither has released it.

Mozilla said why at the time. Apple’s implementation would force it to build and maintain two browsers, “a burden Apple themselves will not have to bear“, a spokesperson said in January 2024.

Microsoft has since put a number on the cost. Its engineers measured a Blink prototype 28.6% faster than WebKit on Speedometer 3.1, on the same device.

Open Web Advocacy wants Brussels to intervene. Apple has “had more than two years to produce a compliant solution“, its director Alex Moore said.

The Commission has not been reticent elsewhere. Apple lost its challenge to gatekeeper designation at the General Court in July.

On the engine, though, nothing has moved. The rule exists, the interface exists, and no rival engine reaches a European iPhone. Microsoft has not shipped a Blink-based Edge either.

Which is what this feature quietly demonstrates. Mozilla built the best blocker Apple’s API allows, in the same year Chrome disabled Manifest V2 extensions including uBlock Origin.