Regex to match JWT

Question

I don't have experience with Regex and I'm asking for your help.

I need a regex to capture the JWT inside the following string:

"contextJwt": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJIZWxsbyB5b3UiLCJuYW1lIjoiV2h5IGFyZSB5b3UgY2hlY2tpbmcgbXkgdG9rZW4_ICggzaHCsCDNnMqWIM2hwrApIiwiaWF0IjoxNTE2MjM5MDIyfQ.yAP0xiTwp6vqIYbLKLVBRv-gTyMvU17rT3H8uErLjHA"

Request answer (2363 lines)

Thanks for your time

Answer 1

I created a regex which might not be the most elegant but it appears to works.

(^[A-Za-z0-9-_]*\.[A-Za-z0-9-_]*\.[A-Za-z0-9-_]*$)

A more concise version could be also:

(^[\w-]*\.[\w-]*\.[\w-]*$)

However, I believe that also non-latin characters would be allowed which would be disallowed as JWT.

Answer 2

I'm answering late as this is still one of the top answers on google for jwt regex and as is often the case, the accepted answers aren't entirely correct.

The minimum encoded base64url output is two characters, so if you want to avoid matching strings like a.a.a (which isn't a JWT) then the following regex is a better alternative:

^[A-Za-z0-9_-]{2,}(?:\.[A-Za-z0-9_-]{2,}){2}$