Most people think that IO Games are those with .io as their top-level domain, but in reality, it’s nothing like that. For example, Little Big Snake has always been a .com domain (and not a .io domain).
IO Game is a genre of games that are made to be played for free on the browser, have minimal controls to follow, is multi-player, and can be played with players from around the globe. Usually, the game has minimal, eye-pleasing graphics, but some IO Games these days can have comprehensive graphics and are also available to download on phones/tablets.
The usual motive of the player in these games is to increase as much as you can– be it in weight, height, or territory. The game remains endless.
No one knows for sure why this particular game genre is called “IO” but it is said that the trend began from the earliest MMO Game Agar.io which had the above-mentioned features, and it was gone viral, after which many more such games developed, like, slither.io, diep.io, cell.io, etc.
.io stands for the internet country code top-level domain– British Indian Ocean Territory. Goggle Advertisements see it as a generic domain. IO also reminds us of Input/Output, a term used in computer science, thus reminding one of all the other geeky terms.