The goal of the game is to breed the longest worm on the server. Slither.io is similar in concept to the popular web game Agar.io from 2015 and resembles a classic arcade game Snake.
The game grew in popularity after being promoted by several prominent YouTubers such as PewDiePie. The browser-friendly version of the game was ranked by Alexa as one of the 2016 most visited websites in July 1.000, while the iOS version ranked first among the most downloaded apps in the App Store. The Android mobile version of the game was released on March 27, 2016. The game's reception was positive, with reviewers praising its appearance and customization, but criticizing it for its low replay value and the high price users have to pay to remove ads.