Best Open Source .io Games to Play, Host, and Mod
Most of the big `.io` games (Agar.io, Diep.io, Slither.io) are proprietary: you can play them, but you can't read their code. Yet a lively open source scene exists for those who want to go further: read the source, host their own server, mod the gameplay, or simply learn how a real-time multiplayer game is actually built.
Why open source .io games are worth your attention
- Learning: a `.io` game is a textbook case of real-time networking — authoritative server, state interpolation, anti-cheat. The code is a goldmine for developers.
- Modding: add your own tanks, rules, or game modes.
- Self-hosting: spin up a private server to play with friends, on your own terms.
Open source .io projects worth exploring
- Woomy-Arras.io: an open source fork of Arras (itself inspired by Diep.io), with fully public code on GitHub. Ideal for hacking on a tank game.
- Fantasy Tank Builder: an open source tank designer, so you can build Diep.io-style machines without starting from zero.
- GitHub clones: countless developers recreate Agar.io or Diep.io as learning projects. Search "io game" on GitHub and you'll find dozens of repos at various levels of polish.
⚠️ These projects are maintained by fan communities: quality and uptime vary, and they have no official connection to the games that inspired them.
Dovion's "zero-dependency" philosophy
Dovion isn't open source, but it takes to an extreme a philosophy that resonates with developers: a Node.js server with zero runtime dependencies (no packages to install) and a world entirely generated by code, identical on every client. We dig into that approach in the behind-the-scenes of a zero-dependency game and the authoritative server deep-dive.
For players, the result is a free, no-download `.io` game that runs even on an older machine. Curious about the diep-like ecosystem? Also read is Diep.io open source? and the Diep.io community.
The bottom line
Open source `.io` is the playground of the curious and the tinkerers. And if you just want to play a lightweight, original `.io` game, jump aboard dovion.io — the code stays in-house, but the fun is very real.