A game demo is a freely distributed demonstration or preview of an upcoming or recently released computer or video game.
Demos are typically released by the game's publisher to help consumers get a feel of the game before deciding whether to buy the full version. For console video games, they are often released with magazines that include the demos on a CD or DVD and likewise may be exclusive to a certain publication. Demos are also sometimes released on cover tape/disks, especially in the United Kingdom and mainland Europe, but given the increasing size of demos and widespread availability of broadband internet, this common practice throughout the 1980s and '90s gradually lost cover focus to full games. With the advent of console online services such as Xbox Live, demos are also becoming available as a free or premium download.
Console manufacturers also often release their systems with a demo disc containing playable previews of games to be released for their console.
Generally, playable demos are stripped down versions of the full game, restricting gameplay to some levels, only allowing access to some features, or limiting the amount of time playable in the game. Usually, demo refers to playable
However, some demos provide content not available in the full game. An example of this was the Age of Empires demo which included a Hittites campaign and two maps not available in the full version. Also, the Half-Life demo Half-Life: Uplink is a self-contained game, adapted from material cut from the development of the main game.
In other cases a demo may differ from the equivalent section in the full game, for instance when the demo is released as a preview before the full game is completed.
Demos for platform or other action games generally only include the first few levels of the game. Demos of adventure games are often limited to a very small number of rooms, and have the "save game" feature disabled. Demos of sports games usually limit play to an accelerated half-time or complete match between a small number of teams (which at the same time led to the practice of "demo expanders" that allow the tweaking of some of those settings). Likewise, demos of racing games are ordinarily restricted to a single race with a pre-selected car.
Today there are many different devices, or platforms, on which games may be played. Personal computers, consoles, handheld systems, and arcade machines are all common. Games are not interchangeable between platforms so, for example, Xbox games will not work in your PC. The 3 main home video game platform companies are Nintendo, Microsoft, and Sony, who between them have created seven of the eight home platforms most commonly used today. The final home platform is the PC.
Many games intended for PCs are now just as prevalent on consoles, with many developers creating versions for more than one platform. During the last generation of gaming, most major PC game releases have coincided with the release of console versions, and titles initially developed for a single platform are often ported to others if they prove to be successful.