Passport Containers by Hrolgar

Passport keeps a list of URL to container rules and opens matching pages in that container. Unlike domain-only assignment, rules match on host and path, so github.com/work and github.com/personal can go to different containers. A regex form (prefix @) sees the query string as well.

The rules and container colours are stored in the extension's sync storage, which Firefox Sync carries with your account. Sign in on another machine, install Passport, and the containers are recreated by name and the rules are already there. Cookies never sync, so you still log in once per container per machine.

Bookmark keywords. Firefox does not let extensions set bookmark keywords. If you sign in with your Mozilla account (optional, Settings > Mozilla account), Passport writes the keyword into the bookmark's Firefox Sync record instead, so it becomes a real Firefox keyword with the address bar's top suggestion, on every device signed in to the account. The sign-in happens on accounts.firefox.com with the standard OAuth flow (PKCE, scoped Sync key); Passport never sees your password and keeps the Sync key on this machine only. Without an account, keywords work through Passport's own address bar handling.

Add a rule, keyword and bookmark for the current site from the toolbar popup, or edit everything on the settings page. The most specific rule wins. Passport collects no data and talks to no server of its own; the only network calls are to Mozilla's account and Sync services when you choose to sign in.