Methods and apparatus, including computer program products, implementing and using techniques for providing user credentials over a network to a remote computer application. User credentials for the remote computer application are stored in a central repository that is accessible through the network. A request is sent to a service to perform, on behalf of a user, a particular task involving the remote computer application. It is determined whether the service has been granted permission to act on behalf of the user with respect to the remote computer application. When the service has permission to act on behalf of the user, the service is used to retrieve the user's credentials for the remote computer application from the central repository and to supply the retrieved user credentials to the remote computer application.