In Agar.io you grow a cell by swallowing both randomly generated pellets, which slightly increase a cell's mass, and smaller cells without being swallowed by larger cells. The goal of the game is to obtain the largest cell; players restart when all of their cells are swallowed by another player. Players can change their cell's appearance with predefined words, phrases, symbols or skins. The more mass a cell has, the slower it will move. Cells gradually lose mass over time.