Agar.io is an online arena game in which you control a small cell and try to become the largest by eating pellets and smaller players. It started as a browser game and has a simple concept that is easy to start and hard to master. This page explains the rules and strategies, along with a few safety notes.

The goal

You begin as a tiny cell in a large arena with many other players. Moving over small pellets increases your size. If you touch a smaller player, you absorb them and gain their mass. If a larger player touches you, you are eaten and the round ends. The aim is to become as large as possible and stay at the top of the leaderboard.

Controls

You move by dragging a finger or using a virtual control, and your cell follows the direction. Buttons allow you to split your cell into two parts, which can be used to catch other players, and to eject small amounts of mass. Larger cells move more slowly, so your speed drops as you grow. This creates a natural balance between size and agility.

Splitting

Splitting is a powerful but risky technique. When you split, one half shoots forward quickly and can swallow a nearby smaller target. However, both halves are smaller and vulnerable, and you may be eaten by a bigger player. Use it when you are confident that the target cannot escape and no larger player is close.

Viruses

Green spiky objects called viruses appear in the arena. Smaller cells can hide behind them, because a large cell that touches a virus splits into many pieces. This can be used as a trap: feeding a virus with mass can make it shoot toward an opponent. Avoid viruses when you are large.

Early-game strategy

Collect pellets in quiet areas and avoid larger players. Stay near the edges where fewer players travel, and gradually move to the centre as you grow. Do not chase small players too far; you could run into a larger one.

Mid and late-game strategy

When you are large, other players become cautious. Move steadily and keep your distance from groups that might coordinate. Be wary of players who suddenly approach, because they may be planning to split. Always consider an escape route.

Teams and modes

Some versions include team modes, in which you cooperate with others to dominate the arena. Communication is limited, so teamwork depends on observing others. Playing on mobile may be less precise than on a computer, so adjust your style.

Safety notes

Nicknames are chosen by players and can sometimes be inappropriate, so parental supervision is advised. The game includes advertisements and optional purchases for cosmetic items. An internet connection is required.