Where the session actually lives

Storage is not one thing. Cookies, local storage, databases, service workers and the cache share one jar, and a page can write to any of them.

So a tool either gives an account a jar of its own or it does not. Emptying a jar afterwards is a different job from keeping two jars apart.

• One jar for everything

  Every tab of the browser reads and writes the same set.

• A jar for the window

  A set that exists while a window is open and goes with it.

• A jar per account

  A set that stays on disk between launches and belongs to one login.

• A jar on other hardware

  A set kept apart because the machine under it is a different machine.

Rows are the approaches and columns are the questions this axis asks. An empty cell means the question does not apply rather than that the answer is bad.

The last row is ours. Every cell in it comes from the launch path in the app, not from a brochure.

Every profile is started in a data directory named after it, so its cookies and storage never meet another profile's. That directory is the whole of the separation.

The engine creates that directory closed to other people on macOS and Linux, and closes it again on every launch. On Windows permissions live in access lists the app cannot set, so we claim no such lock there.

• Cookies and logins

  Written into that directory by the browser and read back only from it.

• Storage and databases

  Local storage, databases and service workers sit beside them.

• The cache

  Kept there too, and left behind when the session travels.

• Browser preferences

  The profile keeps its own settings file in that directory too.

Profiles are processes on your own system and they share it with each other and with you. Anything running under your user account can read those directories.

The browser keeps its own key rather than borrowing one from the system, because a profile has to open on the machine you move it to. On macOS and Linux the directory permissions do the real work.

A session travels either as one encrypted file or through a folder you already sync. Both carry the settings with the browser data, so the account stays signed in on the second machine.

The caches are left out on purpose, and so are the service worker and a few site stores beside them. What keeps the account signed in travels: cookies, saved logins and local storage.

• Sealed with a password

  A wrong password gives a plain refusal instead of damaged data.

• The profile identity travels

  The same profile describes the same machine on the second computer.

• An open profile is skipped

  Copying live databases would deliver a session that does not open.

• Both sides changed means a question

  Two machines worked since the last sync, so neither copy is overwritten quietly.

Deleting a profile moves it to the recycle bin, and its browser data waits there with it. Emptying the bin removes the data directory itself rather than only the row in the list.