Crawl.io

Crawl.io is a game that, as the name suggests, is very similar to Slither.io. You control a tiny snake that becomes larger and larger as it eats the little dots of color scattered all over the place. That said, there are also lots of other snakes (controlled by other players) trying to do exactly the same thing, so it won't be so easy for you.

The idea is very simple: if one snake's head hits another snake's body, it kills it. That means that you have to crawl through the map trying to collect colored dots while also avoiding the attacks of other snakes. Killing another snake doesn't make you bigger just like that, though if you do kill one, you can then eat all the dots that come out of its body.

Crawl.io is a shameless clone of Slither.io, which in turn was strongly based on agar.io. It's thus not very original, but it's still a great game and it can be a lot of fun if you log on when lots of other people are playing too. And fortunately, that's almost always the case.