JWT Decoder
Decode JWT tokens instantly. Inspect payload, header, and signature with detailed analysis.
How to Decode JWT Tokens Online
- Paste your JWT token into the input field or copy from your API response
- Click "Decode JWT" to parse the token
- View the decoded header, payload, and signature separately
- Check the expiration time and token validity
- Verify the token signature with your secret key
- Copy the decoded information for debugging and development
- All processing happens in your browser - your tokens never leave your device
Why Use Our JWT Decoder for Developers
100% Private & Secure
All JWT decoding happens in your browser. Your tokens never leave your device. Perfect for handling sensitive authentication tokens.
Instant Decoding
Decode JWT tokens instantly with no server delays. Real-time token analysis for faster API debugging and development.
Completely Free
No sign-up required, no hidden fees, no limitations. Decode as many JWT tokens as you need, whenever you need.
Developer Friendly
Clean interface with detailed token breakdown. View payload, header, and signature separately for complete token inspection.
Understanding JWT Tokens
📖 What is JWT?
JWT (JSON Web Token) is a compact, self-contained way of securely transmitting information between parties as a JSON object. It's widely used for authentication and authorization in web applications and APIs.
🏗️ JWT Structure
Header: Algorithm and token type
Payload: Claims and user data
Signature: Cryptographic signature
Format: header.payload.signature
🔐 JWT Security
- ✓ Tokens are digitally signed
- ✓ Tampered tokens are rejected
- ✓ Supports multiple algorithms (HS256, RS256, etc.)
- ✓ Can include expiration time (exp claim)
⚡ Common JWT Claims
- sub: Subject (user ID)
- iat: Issued at time
- exp: Expiration time
- aud: Audience
Explore Other Security Tools
While JWT decoding is essential for API development, you might also need other security tools. Here are our other free security and token tools:
Frequently Asked Questions About JWT
What is JWT used for?
JWT is primarily used for authentication and authorization in web applications. When a user logs in, the server creates a JWT and sends it to the client. The client then includes this token in subsequent requests to prove their identity without needing to send credentials each time.
Is JWT secure?
JWT itself is secure when implemented correctly. The token is digitally signed, so any tampering is detected. However, the security depends on: keeping the secret key safe, using HTTPS for transmission, validating the signature, and checking the expiration time.
How do I decode a JWT?
Use our JWT Decoder tool - paste your token and it will automatically parse and display the header, payload, and signature. You can also decode JWTs programmatically using libraries like jwt.io or language-specific JWT libraries.
What does JWT expiry mean?
The "exp" claim in a JWT specifies when the token expires. After this time, the token is no longer valid and authentication will fail. This adds a layer of security by limiting how long a compromised token can be used.
Can I modify a JWT token?
You can modify the content, but if you do, the signature will be invalid. The server verifies the signature to ensure the token hasn't been tampered with. Only the server with the secret key can create valid signatures.
Is my token data secure in your decoder?
Absolutely! All JWT decoding happens entirely in your browser using JavaScript. Your tokens never leave your device and are never sent to any server. We don't store or transmit your token data.
How do I generate a JWT token?
JWT tokens are typically generated server-side using a library specific to your programming language. You need to provide the payload (claims), a secret key, and optionally specify the algorithm. Popular libraries include jsonwebtoken (Node.js), PyJWT (Python), and jose4j (Java).
What is a JWT refresh token?
A refresh token is a long-lived token used to obtain new access tokens without requiring the user to log in again. When an access token expires, the client can use the refresh token to request a new access token, maintaining the user's session securely.
How long should a JWT token last?
Access tokens should be short-lived (5-15 minutes) to minimize security risks if compromised. Refresh tokens can be longer-lived (days to weeks). The exact duration depends on your security requirements and user experience needs.
Can JWT tokens be revoked?
JWTs are stateless and cannot be inherently revoked. However, you can implement revocation by maintaining a blacklist of token IDs (jti claim) on the server, using short expiration times, or implementing a token versioning system tied to user sessions.
What's the difference between JWT and session cookies?
Session cookies store a session ID that references server-side data, while JWTs are self-contained and store all claims in the token itself. JWTs are stateless and scalable but can't be easily revoked. Session cookies require server storage but offer better control and security.
Which JWT algorithm should I use?
For symmetric encryption, use HS256 (HMAC with SHA-256) with a strong secret key. For asymmetric encryption, use RS256 (RSA with SHA-256) or ES256 (ECDSA with SHA-256), which are more secure for public/private key scenarios. Avoid "none" algorithm for security reasons.
JWT Security Best Practices
✅ DO
- ✓ Always validate the JWT signature
- ✓ Check the token expiration time
- ✓ Use HTTPS for token transmission
- ✓ Set appropriate token expiry times
- ✓ Store tokens securely on the client
- ✓ Use strong secret keys
- ✓ Include necessary claims only
❌ DON'T
- ✗ Don't store sensitive data in JWT
- ✗ Don't skip signature verification
- ✗ Don't use weak secret keys
- ✗ Don't transmit over HTTP
- ✗ Don't ignore token expiration
- ✗ Don't trust unverified tokens
- ✗ Don't store tokens in local storage
Learning Resources
jwt.io— Official JWT website with introduction and library list
RFC 7519 - JSON Web Token (JWT)— Official JWT specification
MDN - HTTP Authentication— Authentication concepts and patterns
Auth0 - JWT Learning Guide— Comprehensive JWT guide with examples
JWT Tutorial: Understanding Tokens
JSON Web Tokens (JWT) are an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. JWTs are commonly used for authentication and information exchange in modern web applications and APIs.
How JWT Works
- User logs in with credentials
- Server validates credentials and creates a JWT
- JWT is sent to client (usually in Authorization header)
- Client stores JWT (sessionStorage, memory, httpOnly cookie)
- Client includes JWT in subsequent API requests
- Server verifies JWT signature and decodes payload
- Server authorizes request based on JWT claims
JWT Advantages
- • Stateless authentication
- • Cross-domain authentication
- • Scalable for distributed systems
- • Self-contained with claims
- • Industry standard
Use Cases
- • Single Sign-On (SSO)
- • API authentication
- • Mobile app auth
- • Microservices communication
- • OAuth 2.0 tokens
Security Tips
- • Use HTTPS always
- • Short expiration times
- • Strong secret keys
- • Validate signatures
- • Refresh tokens for long sessions
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