#IDARB is a multiplayer arena ball game set in a 2D platform environment in which players compete on teams to try to score goals utilizing a ball. It supports up to eight players locally. In addition to the base game, players can customize their characters, and create victory songs and team logos via in-game tools. Food recipes can be unlocked by completing achievements, participate in betting on AI games in the Fantasy Gambling mode, and completing a single player mode with a comedic storyline.

A distinct feature of the game, referenced through the hashtag in the title, is the hash bomb, which allows observers to influence in-game events via messages from a user-designated Twitch channel or sent to the Twitter account @idarbwire followed by a four digit unique game identifier. Hash bombs consist of a "#" followed by a word (i.e., a hashtag). The list of supported words has not been released by the developer, leading to much experimentation. After an initial prototype of a red box in a platform environment, the game's content was largely crowd sourced through Twitter messages. The game's name is short for I Drew A Red Box.