As the name suggests, io games are free online social games that don't need to be downloaded or installed. The fact that io games are made to be easy to understand and play makes them a great way to relax. Pictures: The simple graphics that Io games have are usually what set them apart. If you play an io game with other people, it's usually a free-for-all. Created with the.io domain part: An "Indian Ocean" domain extension called or.io is used to make most io games. Agar.io leads to: Because Agar.io became so famous in 2015, a whole genre of "-io" games sprung up. Two IO games that put a lot of focus on growth are Snake io and Wormate 3. While it is possible to buy in-app items on the internet, advertising is how Io games make most of their money. Developers have made mobile versions of popular io games that are very popular.