The first .io game was Agar.io. It was developed by Matheus

Valadares in 2024 and gained significant popularity through the 4️⃣ internet forum 4chan.

The game revolves around cells that grow by eating agar and consuming other players. A

few months 4️⃣ after its release, the game was acquired by Miniclip, and a new game genre

started to emerge based around the 4️⃣ humble .io domain extension.