Where to store user id in jwt

Question

I am generting a jwt for an api token. I am putting the user id into that jwt so I know who is calling into the api. Where do I put the user id in the jwt.

I have seen many different examples that put it in 'sub', 'aud' and even 'iss'. Which is correct if any. Or does user id go in a non registered name?

Answer 1

The sub claim is the right claim for the user identifier. The aud claim identifies the intended recipient of the JWT and the iss identifies the issuer/creator. Any other interpretations of these claims are not standard compliant, see: https://tools.ietf.org/html/rfc7519#section-4.1