The installation is quite simple, although it has one caveat. Here we go:
Step 1: Install my userscript
for Greasemonkey and Tampermonkey (depending on your browser).
That is it! Enjoy playing with your friends! You must play one time and die, so you get to the replay screen and you will see your IP address beneath your score.
Then, a friend can copy this IP address into his connect bar, and press connect. Wait 1 or 2 seconds, and he will automatically join that room.
You can also see your coordinates, so you and your friend can find eachother. Your coordinates are shown in thebottom left.. Check the leaderboard to confirm you are in the same room.
Blocking the JS
This is an easy process if you use AdBlock Plus. Click the AdBlock Plus icon in your bar, and click “Open blockable items”.
Then, right click on the Slither.io js script. This looks like www.slither.io/s/gamexx.js, where xx is the current version.
Anyway, right click on that script, and click Block this item. Then, make sure it’s a blocking filter, select “custom”, and enter http://slither.io/s/game*.js So you have to replace the version number by an asterisk (*). As all shown here.
That is it! Go play with your friends! Feel free to ask any questions. Check the leaderboard to confirm you are in the same room.