Is it normal to have imaginary friends as a teenager?

I don't know if it's common or normal, but it's fine if it doesn't hurt anyone. Including yourself.

I think it can be a legitimate coping mechanism if you're in a legitimately terrible life situation, and a lot of teenagers are stuck in those and trying to bide time until they can age out into adulthood and find somewhere to go where they're really accepted. It's probably not the best scenario but I would mark it as "okay" if you understand why you have imaginary friends now and have a plan for after high school that addresses the issue such that you can make real friends then.

For example, a lot of lesbian/gay/bi kids in homophobic areas may be really socially isolated in high school. If they go to college and join the GSA and meet other like-minded folks, that's all fine. If they graduate high school and get a min wage job in their shitty homophobic hometown and never make any new friends and continue to lean on their imaginary friends for the next several decades, that's very bad news bears.

I think A LOT of teenagers feel like outcasts, and part of that is natural teenage dramatism that will wear off with time and part of that is that high school involves jumbling together a whole bunch of people who don't naturally mesh. It's not weird to feel like an outcast in high school and it's not weird to do what you need to do to survive high school. It only gets weird if it becomes a crutch in adulthood.

I do too

Can’t you make strange internet friends like everyone else