Slither.io is a browser game similar to Agar.io.

Slither.io is a game played inside your browser at the address slither.io. It's compatible with most web browsers.
The game was created like a remake of agar.io, and got extremely (server-crashingly) popular in 2016. The game principles are similar to those of agar.io: your goal is to grow to maximum size by collecting food or eating other players. In slither.io you play as a snake instead of a filled circle, and smaller players can eat bigger ones. The game is free to play and for all.