What are the differences between JWT and OAuth2.0

JWT and OAuth2.0 are two different concepts that are often confused. Here are their differences and relationships:

JWT (JSON Web Token)

Definition

JWT is a token format standard (RFC 7519) that defines a compact and self-contained way to securely transmit information between parties as a JSON object.

Features

• Format Standard: Defines token structure and encoding
• Self-contained: Contains all necessary information, no database queries needed
• Stateless: Server doesn't need to store session information
• Cross-language: Implemented in multiple programming languages

Use Cases

• Authentication
• Information exchange
• Single Sign-On (SSO)

Example

shell
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

OAuth2.0

Definition

OAuth2.0 is an authorization framework (RFC 6749) that defines authorization flows and specifications, allowing users to authorize third-party applications to access their resources on another service without sharing passwords.

Features

• Authorization Framework: Defines authorization flows and roles
• Delegated Authorization: Users authorize third-party apps to access resources
• Token Mechanism: Uses Access Token to access resources
• Multiple Authorization Modes: Supports authorization code, implicit, password, client credentials, etc.

Roles

• Resource Owner: Resource owner (user)
• Client: Third-party application
• Authorization Server: Authorization server
• Resource Server: Resource server

Authorization Modes

1. Authorization Code: Most secure, recommended for apps with backend
2. Implicit: Simple but less secure, for pure frontend apps
3. Resource Owner Password Credentials: Username/password, trusted apps
4. Client Credentials: Service-to-service, no user involvement

Example Flow

shell
User → Third-party App → Authorization Server → Resource Server

Relationship between JWT and OAuth2.0

Key Point

JWT is a token format, OAuth2.0 is an authorization framework

They Can Be Used Together

• OAuth2.0 can use JWT as the Access Token format
• OAuth2.0 authorization flow can return JWT-formatted tokens
• JWT can carry OAuth2.0 claim information

Example: OAuth2.0 Using JWT

javascript
// OAuth2.0 authorization flow
// 1. User authorization
GET /authorize?
  response_type=code&
  client_id=CLIENT_ID&
  redirect_uri=REDIRECT_URI&
  scope=read%20write

// 2. Get Access Token (JWT format)
POST /token
{
  "grant_type": "authorization_code",
  "code": "AUTHORIZATION_CODE",
  "client_id": "CLIENT_ID",
  "client_secret": "CLIENT_SECRET"
}

// Response (JWT format Access Token)
{
  "access_token": "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...",
  "token_type": "Bearer",
  "expires_in": 3600,
  "refresh_token": "REFRESH_TOKEN"
}

// 3. Use JWT Access Token to access resources
GET /api/resource
Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...

Comparison Summary

Feature	JWT	OAuth2.0
Type	Token format standard	Authorization framework
Purpose	Securely transmit information	Authorize third-party access to resources
State	Stateless	Can be stateful
Storage	Client-side storage	Server can store
Revocation	Difficult	Easier
Standard	RFC 7519	RFC 6749
Independence	Can be used independently	Used in combination

Real-world Use Cases

1. Using JWT

javascript
// Simple authentication
const token = jwt.sign({ userId: '123' }, SECRET_KEY);

// Verify
const decoded = jwt.verify(token, SECRET_KEY);

2. Using OAuth2.0

javascript
// Third-party login (like Google, GitHub)
app.get('/auth/google', passport.authenticate('google'));

app.get('/auth/google/callback', 
  passport.authenticate('google', { failureRedirect: '/login' }),
  (req, res) => {
    res.redirect('/');
  }
);

3. Combining JWT and OAuth2.0

javascript
// OAuth2.0 authorization server issues JWT
app.post('/oauth/token', (req, res) => {
  const { grant_type, code } = req.body;
  
  // Verify authorization code
  const authCode = await validateAuthCode(code);
  
  // Generate JWT format Access Token
  const accessToken = jwt.sign({
    sub: authCode.userId,
    scope: authCode.scope,
    client_id: authCode.clientId
  }, PRIVATE_KEY, {
    algorithm: 'RS256',
    expiresIn: '1h'
  });
  
  res.json({
    access_token: accessToken,
    token_type: 'Bearer',
    expires_in: 3600
  });
});

// Resource server verifies JWT
app.get('/api/resource', async (req, res) => {
  const token = req.headers['authorization']?.replace('Bearer ', '');
  
  try {
    const decoded = jwt.verify(token, PUBLIC_KEY, {
      algorithms: ['RS256'],
      issuer: 'https://auth.example.com'
    });
    
    // Check scope
    if (!decoded.scope.includes('read')) {
      return res.status(403).json({ error: 'Insufficient scope' });
    }
    
    res.json({ data: 'protected resource' });
  } catch (error) {
    res.status(401).json({ error: 'Invalid token' });
  }
});

Selection Recommendations

Choose JWT when

• Simple authentication requirements
• Internal system communication
• No complex authorization flows needed
• Single Sign-On (SSO)

Choose OAuth2.0 when

• Need third-party authorization
• Users need to control permissions
• Need multiple authorization modes
• Enterprise applications

Combine when

• Need OAuth2.0 authorization flow
• Need JWT's self-contained feature
• Need cross-service token verification
• Need fine-grained permission control

Common Misconceptions

Misconception 1: JWT can replace OAuth2.0

Wrong: JWT is a token format, OAuth2.0 is an authorization framework, they are concepts at different levels.

Misconception 2: OAuth2.0 must use JWT

Wrong: OAuth2.0 can use tokens in any format, not necessarily JWT.

Misconception 3: JWT is more secure

Wrong: Security depends on implementation, both JWT and OAuth2.0 can be very secure or insecure.

Misconception 4: OAuth2.0 must be complex

Wrong: OAuth2.0 can choose appropriate authorization modes based on needs, not necessarily complex.

Best Practices

1. Understand Requirements: Clarify whether you need a token format or authorization framework
2. Choose Appropriate Technology: Select JWT, OAuth2.0, or both based on scenarios
3. Secure Implementation: Regardless of which technology, pay attention to security
4. Follow Standards: Follow RFC standards and best practices
5. Test and Verify: Thoroughly test authentication and authorization flows

By understanding the differences and relationships between JWT and OAuth2.0, you can make the right technical choices in actual projects.