Walkthrough Guide on Slither.io
At this stage, your itty bitty snake is a very insignificant being. Do whatever it takes to get you to a respectable size. Just go super aggressive at this stage; if you die, just start over because you haven't wasted any time. You want to get out of this stage as soon as possible. I consider 200 to be a size where you can speed boost long enough to kill other snakes without losing significant amounts of body mass. For now, just eat and eat more. Hopefully, some of the bigger snakes won't even consider you worth their time.
Things you might want to consider: Always slither your way towards the middle. That is where all of the action and the BIG snakes are. You can't choose where you spawn, but the map in the bottom right corner should easily guide you towards the middle. Although there is also significantly higher risk in the middle, you came here to have fun, not to slither around safely for eternity.
At this stage, you are primarily doing one thing. Scavenging. Some people may argue against me that doing this is boring, but I personally find it the easiest way to gain body mass at a considerably low risk. After grinding through the early stages of snake life, you really don't want to start from the beginning all over again. So what do I mean by scavenging? First find a "target." I put the target in quotes because you will not be directly attacking the target. What you will be doing is following the target around and around until he makes a fatal mistake. That's when you slurp up all of his body mass for yourself! So what kind of target are you looking for?
The best targets are big, like those monstrous kind, preferably somewhere in the leaderboards. And also aggressive, as they light up a lot, using their speed boost, and they like to circle around smaller snakes to eat them. Nearby and you are able to catch up. Don't bother to always go searching for the perfect target, whatever you find will most likely suffice. What do you do when you find your target? You Follow. That's right you follow. And you don't just plainly follow. Follow their tail. Make sure you never lose sight of the tail. When they boost, you boost; As long as you eat the body mass that your target loses by boosting, you shouldn't lose much yourself. Granted that they are big enough, they will rarely actually see you and will not try to harm you. Remember, you want to find someone aggressive, but that means to you too. If you follow closely enough, no stupid snake is going to want to slither between your target's tail and your head. They will surely either die to your target or to you. When your target finally dies, which you probably had nothing to do with, that's when feeding time starts. Boost. Boost. Boost until you get every single body mass of that huge sad snake.
Alright, you definitely don't want to go for every bit of mass. A very common strategy in slither.io is to simply slurp up big snakes that recently died, meaning that you're going to have competition, most notably the sly Slytherin. A Slytherin that just killed your target for you. This is where reaction speed is crucial. As you boost along the length of the body mass, keep an eye out for another snake boosting in the opposite direction. As soon as you see one, shoot to another direction! Remember that since you are going in different ways, it will require half the reaction speed. Jerk away and slither yourself to safety. Sometimes they might have a slow response, you can probably clean them up too if they hit your body. The advantages to this strategy are pretty significant. Since all killings of bigger snakes occur at the mouth of the snake, that means the killer, who usually has first access to the corpse, will start near the head. But to do that, they need to perform some fancy maneuvers to position themselves to get as much mass as possible. On the other hand, you will be able to see that the snake died at the same time as the killer, except you will already be at the perfect angle to start chomping away. Essentially, you have a huge advantage in collecting body mass over any killer of a huge snake, while they are the ones risking their lives while you sip on tea and munch on speed boosting remains. Once you hit 7000 body mass, this stage is virtually over since it will take longer to find any target significantly bigger than you.
At this stage, you are pretty much big enough to do the best parts of slither.io. You encircle other snakes as you slowly constrain them in a smaller and smaller area around your slithering body, you encircle snakes within snakes, you encircle snakes within snakes within snakes, you get the idea. Make your kills along the way, but again don't be greedy. Take what you can! You should progressively get larger and larger by picking up leftover going from the middle to the outside. Do not be afraid to attack enormous snakes at this point in the game. Big snakes have a horrible turn radius comparing to you, where you are still relatively nimble and agile. If you can get under their nose, they're dead. Do not be afraid to put yourself into a dangerous position to kill a big snake. Killing one big snake on the periphery means you get all of the remains to yourself. It should propel you 3-7k from a single kill.
Size #15000 and beyond
At this stage, you have most likely placed on a respectable spot on the leaderboard. This is the end-game snake. Here is how you get those ridiculous scores around 100k. The hardest part of this stage is making your way to the center of the map safely, and you make the biggest loop you can with no snakes inside. You keep spinning around in that circle, and due to the natural chaos in the center of the map, snakes will be forced to run into you. Do not break your loop, slowly consume snakes that run into you on the next revolution. Your head is invulnerable because you are overlapping your tail 90% of the time, only occasionally breaking your big loop to gather remains. At this point in the game, the upper limit of your score is the upper limit of your patience. I usually grow about 2k every 5 minutes while in the center.