Mozilla has added a built-in ad blocker to Firefox on iPhone. The new feature can block many third-party ads and ad-related trackers before they load, using Apple’s WebKit Content Blocker technology and the EasyList filter. It’s optional and turned off by default. You can enable it from Firefox’s settings under Browsing > Ad Blocker.

Mozilla warns that tougher rules against Google could put Firefox in a difficult position. Google pays browser companies to make Google Search their default search engine, and Mozilla gets much of its revenue from such deals. US regulators want to limit these payments as part of the antitrust case against Google. Mozilla says that could seriously hurt its income and make it much harder to keep Firefox running.

Mozilla today joined the Open Secure AI Alliance, started by @nvidia. Actors from across the spectrum, big and small, even strange bedfellows are coming to a conclusion that Mozilla has championed for years: that open source, and openness is the path forward and needs to be defended. We're glad to be a part of this effort and others that bring together champions for an open source future.

Mozilla is pushing back against UK proposals that could restrict or age-gate VPN services, arguing that VPNs are important privacy and security tools that should not be weakened. The company says VPNs protect users from tracking, cyberattacks, censorship, and data collection, and are widely used by students, remote workers, journalists, activists, and everyday internet users. Mozilla argues this could create privacy risks, as people would need to share personal information to access tools designed to protect their privacy. Mozilla also warned that limiting VPNs would not solve online harm. Instead, governments should hold platforms accountable, improve digital education, and support safer online experiences without weakening internet privacy.

Mozilla used a new AI tool called Claude Mythos to find 271 security problems in Firefox, and all of them have been fixed in Firefox version 150. The team built a special testing system to verify the AI's work. This ensured almost none of the reports were false alarms, as the AI creates simple test pages that run on a special test version of Firefox where a crash proves a real bug The fixed bugs include 180 very serious issues, 80 medium issues, and 11 small issues.

We partnered with Mozilla to test Claude's ability to find security vulnerabilities in Firefox. Opus 4.6 found 22 vulnerabilities in just two weeks. Of these, 14 were high-severity, representing a fifth of all high-severity bugs Mozilla remediated in 2025.

Open-source AI is closing the gap. Mozilla's latest report finds the average capability gap between the top open and closed AI models has narrowed to just 3.3%, down from more than 8% in early 2024. What does this mean for the future of AI? Join @raffi and Rest of World's Deputy Editor Itika Sharma Punit as they unpack the findings, what they reveal about the AI race, and what's happening beneath the headlines. Watch here:

Open models are ~50x cheaper than closed ones. Mozilla CTO @raffi talks about the economics of open source AI, the "amnesiac" problem with agent memory, and why concentration risk isn't just about who's closed — it's about who's open, too. Read/watch here:

The GPT-6 Astra launch just leveled up game development. It also gave Mozilla CTO @raffi Krikorian an idea for an open-weight experiment. One prompt. Six open-weight models. Four coding harnesses, identical instructions. Read what happend when he ran it on Owners, Not Renters. Subscribe today.