Firefox 148 introduces the promised AI kill switch for people who aren't into LLMs

Mozilla has rolled out its anticipated "AI kill switch" in Firefox 148, giving users definitive control over browser interactions with large language models. This feature arrives as a direct response to growing privacy concerns and computational demands of embedded AI systems across Windows, macOS, Linux, Android, and iOS platforms.

The implementation blocks all browser-initiated connections to LLM services at the network level. When activated through about:config (desktop) or advanced settings (mobile), it prevents:

1. AI-powered form assistance and content suggestions
2. Real-time translation engines using cloud-based models
3. Context-aware search enhancements
4. Background data collection for ML training

Desktop users toggle the feature via browser.ai_block.enabled boolean flag, while Android/iOS implementations synchronize the setting through Firefox accounts. The mobile implementation required specific attention due to platform limitations on background processes - Android leverages custom WebView restrictions while iOS uses content blocking rules.

For developers, this introduces new compatibility considerations. Feature detection scripts should now verify navigator.aiBlockEnabled before invoking AI APIs. Mozilla recommends implementing graceful fallbacks, as approximately 17% of Firefox users are projected to activate the setting based on early beta data.

The kill switch operates independently of existing tracking protections, focusing exclusively on generative AI endpoints. Mozilla's documentation notes known conflicts with some educational and accessibility extensions that rely on LLMs, advising extension maintainers to declare explicit permissions in manifest v3.

Performance metrics from nightly builds show measurable impact: Pages using heavy LLM integrations load 22% faster with the blocker enabled, while memory usage drops by up to 15% on complex sites. The trade-off eliminates all browser-mediated AI features without affecting traditional scripting.

As LLM integration becomes ubiquitous, this delivers concrete privacy controls absent in Chromium-based browsers. Firefox's approach sets a precedent for user agency in the AI era - one that doesn't require compromising core functionality for those prioritizing performance and data sovereignty.

Firefox 148 Release Notes | AI Blocking Technical Documentation