JWT vs Opaque Token: Key Differences and Use Cases

In distributed systems, web apps, and APIs, tokens are frequently used for authorisation and authentication. JWT (JSON Web Token) and opaque tokens are the two most popular kinds of tokens. Here is a detailed comparison of the two, including their benefits, drawbacks, and application cases.

What is a JWT (JSON Web Token)?

A JWT is a self-contained, encoded token that contains information (claims) about a user or entity. It’s digitally signed using a secret (HMAC) or a public/private key (RSA or ECDSA) to ensure data integrity and authenticity.

Structure of a JWT
A JWT consists of three parts, separated by dots ( . ):
1. Header: Metadata about the token, such as the signing algorithm.
2. Payload: Contains claims (e.g., user ID, roles, expiry).
3. Signature: Verifies the integrity of the token.

Example JWT:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ
.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Key Features of JWT

• Self-contained: All the information (claims) required for authentication is included in the…