Can a person go to a private repl's domain?
So let's say I'm working on a project called 'example' in html. Can someone else go to example.p1ckl3.repl.co ? If so, is there a way to prevent this?
yes. They can.
You can't prevent it. The code is 'hidden' but that's it. Just name your repl something that is very very hard to guess because the name won't be public so the website can't be exactly found.
Actually, there is a way to prevent this. For example, if you are doing this in Python, follow the following code:
By the way, can you mark this as answered? That way, people know that this is correct. In Python technically, you can do this :P, but in this case its only preventing Cookie from viewing it. You can do this to other stuff, too.