Length is one of the most important aspects of Slither.io. The length of your snake, which also determines its size, is displayed as a number in the lower left-hand corner of the screen. To increase your snake's length you must eat pellets, either those randomly generated by the game (which give a small amount of length), pellets left from speed boosting (small amount of pellets) or by eating the remains of other unlucky snakes who have died (typically giving much more length than individual pellets).
Snakes will lose length when they use their movement boost.
The length of a snake also determines its turning speed and radius. The bigger the snake, the slower the turning speed is and thus turning radius is larger. The snake continues to grow larger in length and thickness until it reaches the maximum length of about 40,000 mass. After this point the score will increase but the size of the snake will stay the same.
The player's vision is also affected by their snake's length, with the camera gradually zooming out the bigger they become up to a certain distance. Note that camera zooms out slowly so new players still have small vision for some time even after they've eaten a lot.
Ranking and Leaderboard
Along with your current length, you are also shown where you rank among other players on the server. Typically this is shown as "X of Y Players" where X is your current rank and Y is the total number of players in your game.
The Leaderboard shows the current lengths and names of the top 10 longest snakes in the game.