Bungie initially conceived ODST as a small side project to produce in the lull between Halo 3's completion and Halo: Reach. Instead of featuring recognizable characters such as armored protagonist Master Chief, the developers focused on the ODSTs. Story director Joseph Staten penned a detective story utilizing film noir designs, settings, and characters. Composer Martin O'Donnell abandoned his previous Halo themes to create a quieter, jazz-influenced sound. During development, the planned expansion grew in scope to that of a full-sized game. Release marketing for the game included a tie-in comic, live-action trailers, and print and web advertisements.
Upon release, ODST became the top-selling Xbox 360 game worldwide. The title received generally positive reviews from critics, who praised the atmosphere, music, and story approach. Reviewers were divided on whether the relatively short campaign and included extras were enough to justify the game's US$60 price tag. The game was the top-selling title in the United States in September 2009, and sold more than 3 million copies worldwide. Softpedia, Time and Wired were among the publications that declared the game one of the year's best.