[html] What characters are valid in a URL?

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Which characters make a URL invalid?

I'm trying to remove the non-URL part of a big string. Most of the regexes I found are like [A-Za-z0-9-_.!~*'()], but there are more things that can a url contain. Like http://127.0.0.1:8080/test?v=123#this for example

So what are the latest characters for a valid URL?

All the gory details can be found in the current RFC on the topic: RFC 3986 (Uniform Resource Identifier (URI): Generic Syntax)

Based on this related answer, you are looking at a list that looks like: A-Z, a-z, 0-9, -, ., _, ~, :, /, ?, #, [, ], @, !, $, &, ', (, ), *, +, ,, ;, %, and =. Everything else must be url-encoded. Also, some of these characters can only exist in very specific spots in a URI and outside of those spots must be url-encoded (e.g. % can only be used in conjunction with url encoding as in %20), the RFC has all of these specifics.