The first .io game was Agar.io. It was developed by Matheus Valadares in 2015 and gained significant popularity through the internet forum 4chan. The game revolves around cells that grow by eating agar and consuming other players. A few months after its release, the game was acquired by Miniclip, and a new game genre started to emerge based on the humble .io domain extension. 

The games that followed were focused on the growth mechanics that made Agar.io so popular, strengthening the idea of .io as a genre, not just a domain extension. Paper.io was one of those games, with the same simple yet addictive concept. There are now many grow games like Snake.io and Holey.io, taking this fast-paced survival concept further.

Many .io games are based on survival - growing your character by consuming food and slaying other players. Reach the top of the leaderboard by doing this repeatedly until you're the biggest! Most IO games feature:

.io games have grown substantially to include any and every type of game, from egg-shattering FPS games like Shell Shockers and Krunker.io to survival battle royale games like Voxiom and Zombs Royale.

Some of the newest .io games include Smash Karts and the fantastically futuristic FPS game, Ev.io. Check out Pixel Warfare and Bloxd for two of the newest and most fantastic .io games available.

Most .io games work seamlessly on mobile devices and desktop, since the controls are easy to learn. Browse the full collection on this page for all IO games, and be sure to check back regularly for the latest and greatest browser-based .io titles!

IO games are real-time online games you can play in your web browser for free. The most common theme among .io games is online multiplayer. Besides that, these games are mostly based on the domain extension .io, which stands for ‘Indian Ocean.’ The top level domain extension is popular with software engineers since IO is short for 'Input / Output', a common term in computing.