Firefox Multi-Account Containers are one of the browser's most powerful privacy features. Most users know the basics — here's what you can do with them beyond the defaults. Quick Refresher Multi-Account Containers isolate websites into separate "containers." Each container has its own cookies, localStorage, IndexedDB, and cache. A site in Container A can't see cookies from Container B. Think of each container as a separate browser profile, but all within the same Firefox windo...