"Slither.io" is a web massively multiplayer online game released in 2016, developed by Steve Howse. In the game, the player must control a worm-like creature and capture various colored dots to increase its size. The ultimate goal of the game is to become the largest worm on the server. The game concept of "Slither.io" is similar to that of the popular web game "Agar.io" in 2015 and the classic arcade game "Snake" mode.

The web version and iOS version of the game were released on March 25, 2016, and it was popularized by many well-known YouTubers such as PewDiePie. Soon after the game was released, "Slither.io" topped the list of free software sales in the App Store in various regions, and the web version was ranked as the 250th most viewed website in the world by Alexa in July 2016. The Android version was launched on March 27 of the same year. "Slither.io" received mostly positive reviews. Its gameplay and design have been praised by critics, but advertising and delays have been criticized.

In the game, the player controls a worm-like creature, looks for and captures dots of various colors on the map to make it larger, and at the same time annihilates other players to obtain more dots, striding towards the goal of becoming the largest worm in the entire server[1]. If the head of the player’s worm touches another player’s worm, the player will die. The player's corpse will turn into very bright and very large dots. The color of these dots corresponds to the color of the player's worm. When the player presses the left mouse button or the space button, the worm's moving speed will increase, but at the same time it will make the body smaller, and dots will appear on the route where the worm has moved quickly. Moving quickly helps to eliminate other players. Another strategy for defeating other players is to rotate around the opponent until the opponent is trapped in a circle surrounded by the player's body and cannot escape, and finally hits the player's body. The map has a boundary. If the player hits the boundary, it will disappear without leaving a dot. As of 2016, at the end of the day, the largest worm on the entire server can send a "victory message" to the world.