Among Us was inspired by the live party game Mafia,[5][26] and the science fiction horror film The Thing.[27] The idea for the concept was originally given by Marcus Bromander, co-founder of Innersloth, who had played Mafia since he was a kid. In the original game, function cards were dealt and players wandered around a house, aimlessly, while another person secretly killed the players, drawing a finger around their neck. Most of its mechanics were still present in Among Us, but the team wanted to "alleviate the need to create an interesting home model and have someone wandering around in a boring environment". So, they decided that the game would be space-themed and also added tasks, which, according to Forest Willard, programmer at Innersloth, "changed several times during development".[27][28]
Development began in November 2017.[28] The game was initially intended to be a mobile-only local multiplayer game with a single map.[29] Bromander paused development on Innersloth's other game, The Henry Stickmin Collection, in order to build Among Us' first map, The Skeld.[30] When they began developing the first map, they intended that the ship was always in crisis and that the Impostors could do tasks. However, they found this setup "stressful" and decided that it "[would not leave] much time for detective work and informed meeting conversations".[27][28] Willard described playtesting as painful and frustrating, as the game would break down during sessions forcing him to send playtesters new builds off of Google Play. The team tested the game with 8 of their friends and never tested the game with 9 or the maximum of 10 players.[30] The game was developed using the Unity engine.[31]
The game was released in June 2018 to Android and iOS under the AppID "spacemafia".[5] Shortly after release, Among Us had an average player count of 30 to 50 concurrent players.[23] Bromander blamed the game's poor release on Innersloth being "really bad at marketing".[29] The team nearly abandoned the project multiple times but continued work on it due to a "small but vocal player base",[32] adding in online multiplayer, new tasks, and customization options.[32] The game was released on Steam on November 16, 2018.[1] Cross-platform play was supported upon release of the Steam version.[33] Originally, the game had no audio to avoid revealing hidden information in a local setting,[h] and Willard mixed sounds from numerous sound packs to compose the SFX during the game's Steam rele