ClavisPass for Firefox communicates with the local ClavisPass desktop app through Firefox Native Messaging.

The extension reads the active website domain to ask the local desktop app for matching vault entries. When the user chooses to fill a login, the extension requests the selected login data from the local desktop app and inserts it into the active page.

The extension does not send passwords, vault contents, browsing history, or website data to Arratel or other remote servers. Data exchanged by the extension is used only for local pairing, matching, autofill, and save/update prompts with the ClavisPass desktop app.