BrowserQuest is browser based game and thousands of simultaneous players can play the game. It has an in-game chat to interact with other players and it also allows you to team up with other players to fight enemies together.
BrowserQuest is available across different browsers and platforms. It can played on Firefox, Chrome and Safari. Opera can also be used to play the game WebSockets enabled. It is compatible with iOS, Android devices running Firefox. The game is released under open source, source code can be found on GitHub.