Both JWT and OAuth 2.0 are used for managing authentication and authorization, but they serve different purposes and work in distinct ways.

1. Purpose:

• JWT (JSON Web Token):
  • JWT is a compact, URL-safe token format used to securely transmit information between parties as a JSON object.
  • It is typically used to authenticate users and share information between services. It can carry information about a user, session, or any other kind of data.
  • JWT can be used independently or in conjunction with other protocols, such as OAuth.
• OAuth 2.0:
  • OAuth 2.0 is a framework for authorization. It allows a user to grant third-party applications limited access to their resources without sharing their credentials.
  • OAuth defines roles (Resource Owner, Client, Authorization Server, and Resource Server) and flows (Authorization Code, Implicit, Client Credentials, etc.) to allow different types of applications (web, mobile, etc.) to access user data securely.

2. Role:

• JWT:
  • Primarily used to represent claims or information in a compact and self-contained format.
  • It’s a token that can carry authentication and authorization data. Once the user logs in, a JWT is often issued and used in subsequent API requests to verify the user’s identity.
• OAuth 2.0:
  • OAuth is a protocol that delegates access to resources by issuing tokens (which could be JWT) to clients, allowing the client to access the resource on behalf of the user.
  • OAuth 2.0 does not define the format of the access token, meaning the access token could be in JWT format, but it could also be other formats (like opaque tokens).

3. Token Format:

• JWT:
  • A JWT is a token format itself. It consists of three parts:
    • Header (metadata about the token),
    • Payload (the claims or data being transmitted),
    • Signature (used to verify the integrity of the token and ensure it hasn’t been tampered with).
  • JWT can be used independently for various purposes like authentication, information exchange, etc.
• OAuth 2.0:
  • OAuth 2.0 is a protocol for authorization. It doesn’t dictate the token format, so the access token could be a JWT, an opaque token, or another custom format.
  • OAuth provides the framework to obtain and validate these tokens, but doesn’t specify how the token’s content is structured.

4. Authentication vs Authorization:

• JWT:
  • Authentication: JWT is often used for authentication, particularly in the context of a web application or API. Once a user is authenticated, a JWT can be sent to the client (e.g., browser or mobile) and used for subsequent requests to prove that the user is authenticated.
  • While it can carry authorization data (like roles or permissions), JWT itself is more commonly used to confirm a user’s identity.
• OAuth 2.0:
  • Authorization: OAuth 2.0 is specifically designed for authorization. It allows users to grant applications (clients) access to their resources (like Google or Facebook data) without sharing their login credentials.
  • OAuth 2.0 does not authenticate users directly. Instead, it allows third-party apps to access a user’s data using access tokens, usually issued by an Authorization Server.

5. Flow and Usage:

• JWT:
  • After a user successfully logs in (typically using credentials like username and password), a JWT is issued by the authentication server.
  • The JWT can then be included in subsequent API requests, usually in the HTTP Authorization header (using the Bearer scheme), allowing the server to verify the user’s identity without needing to check a database each time.
• OAuth 2.0:
  • In an OAuth flow, the user logs in and grants permission to a client (application) to access resources.
  • OAuth 2.0 handles the authorization step and issues an access token (which could be a JWT). This access token is then used by the client to make requests to the resource server.
  • OAuth defines several different “flows” to handle various situations, such as client credentials or user consent.

6. Token Expiry and Revocation:

• JWT:
  • JWTs often have an expiration time (usually defined within the payload in the exp field). Once the token expires, the user needs to reauthenticate or refresh the token.
  • JWTs cannot be revoked (unless you implement a blacklisting mechanism). They remain valid until they expire.
• OAuth 2.0:
  • OAuth 2.0 tokens (like access tokens) also have an expiration time. However, OAuth allows for refresh tokens that can be used to obtain a new access token without re-authenticating the user.
  • OAuth 2.0 supports revocation. Access tokens can be revoked by the authorization server, providing more control over token lifecycle management.

Summary of Differences:

In summary, JWT is a token format, whereas OAuth 2.0 is an authorization framework. OAuth 2.0 can use JWT as the access token, but JWT on its own is used for different use cases, primarily for authentication and information sharing.