Tails

Tails starts a separate operating environment from a USB stick instead of running a private browser inside the normal desktop session. It uses Tor networking and includes document and communication tools. Decide what should survive shutdown: the Persistent Storage feature keeps selected files and settings in a passphrase-protected encrypted partition, which can be left locked at startup. The documentation explicitly says that partition is not hidden from someone holding the USB stick. Plan backups for work that matters and read the operating limitations before relying on a session for sensitive activity.