Methods and systems to identify a user across multiple browsers and machines are described. In some embodiments, a web request is received at a retrieval service from a browser. The web request may include a request to access a retrieval service website of the retrieval service and may be initiated by a redirection of the browser from a requesting service to the retrieval service. A unique identifier associated with a user logged in to an account of the retrieval service may be determined. The user may be logged in to the account via the browser. A redirect request is sent from the retrieval service to the browser. The redirect may include the unique identifier and may redirect the browser from the retrieval service website to the requesting service. The unique identifier may be used by the requesting service to perform additional functionality specific to the user.