Where to find a list of what is allowed in a url

Not a Wappler specific question, but I am working on a job with many languages and need to get dynamic urls in some parts, but some names have funny characters like the crunchy ae in Lyngvær, as a destination.

Question 1, is there a list somewhere that tells me what is allowed in a url and what is not.

Question 2, is there possibly a replacement script that would be smart enough to map out all bad characters to good ones so I never land up with encoded urls like Lyngv%C3%A6r and rather it swaps out crunchy æ with just ae.

By the way crunchy æ is called a diphthong, I learned that today.