My Minecraft keeps crashing whenever I try to play

Whenever I try to play on a multiplayer server or play on one of my worlds, it crashes. I even try to uninstall it and download it again, but it still crashes. I'm not sure if it is because I downloaded too many mods on my computer or if it's something else. (I wasn't using any mods at the time) (I am also not sure of the Version, but I'm pretty sure it is the one I selected.)