How to work with JWT? I don't understand it

I don’t understand JWT.
I knew something from the internet about it:

  • It provides secure api calls
  • It ensures that the data didn’t changed in the air
  • It authenticates api calls

But what i can’t understand:

  • How to let my user know his token.
  • How to send a request to the server with token (post/get/or whatever)
  • Any alternatives?

JWT does not say anything about this. It specifies the format of the token, what it contains, and how it is encrypted or signed.

An application that I build uses these steps:

  • The user navigates to a login page.
  • He enters username and password, submits the login form.
  • The server validates username and password.
  • If they are correct, the server creates a JWT for the user.
  • The server sets a cookie on the response.
  • The browser of the user stores the cookie and sends it on any future request to the server.
  • The server extracts the JWT from the cookie send by the browser.
  • The server validates the JWT (signature OK, did not expire) to know if the user successfully authenticated.
  • If necessary, the server checks additional claims made in the JWT to decide if the user is allowed to access the requested resource.

I also use JWTs for server to server communication. The receiving server acts like described above. But the requesting server can not login. So I generate a long lived JWT and store it in the configuration of the requesting server.

There are two alternatives:

  • The HTTP header Authorization: Bearer <token>
  • A HTTP cookie (which is also send in a HTTP header)

It is up to the server to retrieve the JWT from these HTTP headers.

None that I know of. JWT is a fine technology. They are easy to understand, extensible, supported by many programming languages, easy to use in web applications.


You might find my article on JWT and OpenID Connect helpful.

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