How to get the claims from a JWT in my Flutter Application

Question

I am writing a Flutter/Dart application and am getting a JWT back from an auth server that has some claims I need to use. I have looked at various (4 so far) Dart JWT libra

Answer 1

As of this writing, the jaguar_jwt package is being actively maintained. Although it is not clearly documented, it does have a public method that will decode Base64Url encoding. It does basically the same thing as the accepted answer.

//import 'package:jaguar_jwt/jaguar_jwt.dart';

final String token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1NTQ4MjAxNjIsImlhdCI6MTU1NDc3Njk2MiwiaXNzIjoiU3VyYWdjaCIsInN1YiI6IjQifQ.bg5B_k9WCmxiu2epuZo_Tpt_KZC4N9ve_2GEdrulcXM';
final parts = token.split('.');
final payload = parts[1];
final String decoded = B64urlEncRfc7515.decodeUtf8(payload);

This gives a JSON string, which for this particular example is:

{
  "exp":1554820162,
  "iat":1554776962,
  "iss":"Suragch",
  "sub":"4"
}

See also:

• JWT: The Complete Guide to JSON Web Tokens
• String based data encoding: Base64 vs Base64url