Firefox 153 makes Containers opt-out with 4 pre-configured tabs

Mozilla has pushed a significant privacy and security upgrade with Firefox 153, making Containers an opt-out feature rather than opt-in. Containers isolate browser tabs so cookies, session data, and site interactions from one container cannot leak into another. This prevents malicious sites from fingerprinting users or accessing sensitive data from other tabs. Firefox now ships with four pre-configured containers: Personal, Work, Banking, and Shopping. Users can also create custom containers, and a new setting (Settings > Tabs and browsing > Manage settings) lets users choose a container for every new tab they open.

Additionally, Firefox 153 introduces experimental local network access restrictions. When a website attempts to connect to devices on the user's local area network — such as routers, printers, smart TVs, or IoT devices — the browser will now prompt for permission. This counters a common attack vector where malicious sites scan or communicate with local hardware without consent. The feature is rolling out slowly and can be managed under Settings > Permissions and data. Together, these changes make Firefox one of the most privacy-conscious mainstream browsers without requiring a full switch to Tor.