AuthRelay от JoyfulCoders

AuthRelay lets you sign in with Google on desktop browsers using your Android phone — no passwords typed on the desktop, no credentials stored on any server.

How it works:

Visit any site with Google sign-in. AuthRelay detects the OAuth page automatically.
Click the extension icon and scan the QR code with the AuthRelay Android app.
Authenticate on your phone. Your desktop browser completes sign-in instantly.
Key features:

End-to-end encrypted — the relay server never sees your credentials
Zero-knowledge architecture — only encrypted blobs pass through the server
Ephemeral sessions — sessions expire automatically, nothing persists
Fully open source under the MIT License
No account required, no tracking, no bloat
Requirements:

AuthRelay Android app (free on Google Play)
A relay server (self-host or use the default)