Mattel offers an official multiplayer version of Uno known as UNO & Friends, which can be played online on Facebook or downloaded as an app to play on Android or iOS devices. Gamers2Play.com, AGame.com and Unoooo.com also offer online multiplayer versions of Uno.
Connect with a Facebook account to play UNO & Friends online for free. Create games and invite friends to play along, or play against Facebook users worldwide. Download the smartphone app to play multiplayer matches on-the-go over 3G or Wi-Fi.
Gamers2Play.com and AGame.com host the same version of the game, complete with game instruction. Unoooo.com has two different online versions of the game to choose from, as well as a page of the game rules.