Agar.io is a simple but wildly addictive browser-based multiplayer game. On agaronline.io you can play it for free, instantly — no download, no installation, just jump right in and start competing. 

What is Agar.io

In Agar.io, you control a small circular “cell” floating in a huge Petri-dish–style arena. The goal is to eat pellets and smaller cells to grow bigger — while avoiding being eaten by larger cells controlled by other players. 
As you grow, you become slower — and more powerful — but also more vulnerable if you make a mistake.

How to Play

  • Use the mouse (or finger on mobile) to control the movement of your cell. 

  • Press Spacebar to split your cell — this can help you catch smaller, faster cells or escape danger. 

  • Press W to eject a bit of your mass — useful for feeding teammates, tricking enemies, or manipulating the mechanism of “viruses” (spiky green obstacles) in the game.

Game Modes & Variety

agario offers multiple modes to keep gameplay fresh:

  • Free-For-All (FFA) — classic mode where it's every cell for themselves. 

  • Teams — cooperate with others to dominate the arena. 

  • Battle Royale / Experimental / Party modes — various twists that change the rules, often introducing new mechanics or team-based strategies. 

Why Agar.io Still Rocks

  • Instant and accessible — since it runs in browser, you don’t need to install anything. Works on both PC and mobile. 

  • Easy to learn, hard to master — basic mechanics (move, eat, split) are intuitive, but becoming the biggest cell ever requires strategy, reflexes and patience. 

  • Massively multiplayer & unpredictable — thousands of players join in real time; every match is different, with ever-changing alliances, rivals, and challenges.

  • Fast-paced but casual-friendly — you can play a quick round in a few minutes, or grind for dominance — whatever mood you’re in.

Tips & Strategy Highlights

  • In early game — stay small and safe. Eat pellets and avoid bigger cells until you’re strong enough.

  • Use the split (Spacebar) strategically: split to catch smaller prey, but don’t over-split if you’re vulnerable.

  • Use eject mass (W) wisely — to feed teammates, bait opponents, or manipulate virus mechanics.

  • Keep awareness: watch the map, avoid crowded zones, and stay alert — bigger cells move slower, but when they strike, they hit hard.