This is a list of all the current server IP addresses.
If you reload the game it will connect to a faster server that the game automatically picks for you, and you have the least lag possible. Keep in mind though that it is still lagging, because the game is constantly growing. The developers are trying to fix this by adding more servers, so just be patient and it will be solved.
Make sure you disable any other slither.io extension and scripts first!
How to install user scripts?
Firefox and related browsers: Greasemonkey.
Google Chrome, Chromium, and related browsers: Tampermonkey.
Opera (version 15 and later): Tampermonkey or Violentmonkey.
Opera version 12 and earlier supports user scripts natively. Violentmonkey provides a friendlier UI and better compatibility.