What's the deal, .io?

Accessible multiplayer simplicity.

Chances are, you've stumbled across a number of games with ‘.io’ at the end of their names. But what do those two little letters actually mean?

To find out, you’ll need to rewind a few years to when a game called hit the scene. The goal was simple: consume small orbs and avoid the larger ones. The hook: each of these circles represented actual players somewhere in the real world. Except they weren't simply circles, but cells in a petri dish just, you know, less icky.

“It started with me just playing with the way I could render cells,” said's then 19-year-old creator Matheus Valadares, explaining how the wobbly motion of cells under a microscope (agar is the jelly used to cultivate bacteria) was his initial creative spark. “I got [these circles] to look like they do in now, and thought: ‘Hey, that looks cool. Let’s make a game with those.’”

Each and every cell in is a live human player trying to dominate the arena.

In just a few short months,'s rapid popularity inspired a slew of new ‘.io’ games from other developers. As well as retaining Valadares’ core ideals, many of them took that seemingly innocuous suffix and ran with it. Two strikes of the keyboard that were quickly defining their own gaming genre.

In – and games inspired by it – you grow larger and stronger than other players the longer you survive. On the flip side, being big and powerful makes you more attractive to your opponents, because the rewards for your demise are huge., one of the first successors to arrive after, challenges players to manoeuvre a snake as it grows to unwieldy sizes. Following that, put players in an arena of six-sided tiles to try to claim larger clusters by drawing perimeters around them.

The more successful you are, the bigger a target you become.

Matheus Valadares, creator of

Crash of Cars, a multiplayer game that landed on the App Store this year, can be considered a ‘.io’ game even without the branding. It combines all the aesthetics and upgrades it with a rich visual experience. Its multiplayer combat continues that simple .io goal of dominating the opposition, while enhancing it all with stunning graphics and impressive effects.

“Like, they’re generally very accessible games with simple controls and goals,” Valadares said. “The more successful you are, the bigger a target you become.”

Even Valadares’ follow-up game continued the trend he started in engaging multiplayer gameplay with simplistic visuals. In, players level up and battle tanks in a simply designed, persistently multiplayer arena. “ only took about two or three weeks to develop,” he explained.

Even without the suffix, Crash of Cars is an ‘.io’ game at heart.

So started a trend, but what do those two letters actually mean? Well: “Agar is a medium in which cells are cultivated,” explained Valadares. "The ‘.io’ was just the domain I used for the web game. It was easier to get a short [name] like that.”

While the story behind the genre-defining suffix might be somewhat anticlimactic, the impact that single game has had is far from it.

“It’s been pretty amazing to see casual massively-multiplayer online games like this becoming a thing,” Valadares told us. “To have something that started from quite small beginnings become a game played by millions – and a number 1 app – is something I didn’t really see coming.”

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