Inspired by the popular OmniAuth, OmniContacts is a library that enables users of an application to import contacts from their email or Facebook accounts. The email providers currently supported are Gmail, Yahoo and Hotmail. OmniContacts is a Rack middleware, therefore you can use it with Rails, Sinatra and any other Rack-based framework. OmniContacts uses the OAuth protocol to communicate with the contacts provider. Yahoo still uses OAuth 1.0, while Facebook, Gmail and Hotmail support OAuth 2.0. In order to use OmniContacts, it is therefore necessary to first register your application with the provider and to obtain client_id and client_secret.