StringOps.ai - Free String Operations Tool
JWT Operations
Decode, analyze, and work with JSON Web Tokens (JWTs) securely. Essential tools for understanding token contents, debugging authentication issues, and validating JWT structure.
Client-Side Processing
All JWT operations are processed entirely in your browser. No data is sent to external servers or stored anywhere:
- JWT decoding happens locally in your browser
- No network requests are made during processing
- Your token data never leaves your device
- Processing works completely offline
Try JWT Operations Now
Decode and analyze JWT tokens instantly with our secure tools.
Open StringOps ToolUnderstanding JWT Structure
A JWT consists of three parts separated by dots (.), each Base64-encoded:
Header
Contains algorithm and token type
Payload
Contains claims and user data
Signature
Verifies token integrity
Decode JWT
Decode a JWT token to view its header, payload, and signature components in human-readable format. This operation only decodes the Base64-encoded parts without signature verification.
Example Decoded JWT:
Header:
{
"alg": "HS256",
"typ": "JWT"
}Payload:
{
"sub": "1234567890",
"name": "John Doe",
"iat": 1516239022,
"exp": 1516242622,
"aud": "my-api",
"iss": "auth-server"
}Signature:
SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
Use Cases:
- Debugging authentication issues
- Inspecting token claims and expiration
- Understanding token structure
- Validating token format
- Educational purposes and learning
Extract JWT Claims
Extract and display specific claims from a JWT payload in an organized format. This helps identify user permissions, expiration times, and other critical information.
Common JWT Claims:
Extracted Information:
- Token expiration status (expired/valid/future)
- User identity and roles
- Token permissions and scopes
- Issuer and audience validation
- Custom application claims
Encode JWT Payload
Create a JWT token from a JSON payload. This operation creates an unsigned JWT for testing purposes. Note: The generated token is not cryptographically signed and should only be used for development and testing.
Development Only: Tokens created with this tool are unsigned and should never be used in production applications. They are intended for testing, learning, and development purposes only.
Example Input JSON:
{
"sub": "user123",
"name": "John Doe",
"email": "john@example.com",
"roles": ["user", "admin"],
"iat": 1700000000,
"exp": 1700003600
}↓ Becomes an unsigned JWT token for testing
Use Cases:
- Creating test tokens for development
- Mocking authentication in tests
- Learning JWT structure and format
- Prototyping authentication flows
- Testing JWT parsing libraries
JWT Security Best Practices
✅ Do
- Always verify JWT signatures in production
- Set appropriate expiration times
- Use strong signing algorithms (RS256, ES256)
- Store secrets securely
- Validate all claims before trusting
- Use HTTPS for token transmission
❌ Don't
- Store sensitive data in JWT payloads
- Use weak algorithms (none, HS256 with weak keys)
- Ignore expiration times
- Trust unsigned tokens
- Share tokens over insecure channels
- Use the same secret for multiple applications
JWT Validation Checklist
- ✓ Verify signature with correct key
- ✓ Check token expiration (exp claim)
- ✓ Validate issuer (iss claim)
- ✓ Confirm audience (aud claim)
- ✓ Check not-before time (nbf claim)
- ✓ Validate custom claims
- ✓ Ensure algorithm matches expected
- ✓ Handle token revocation if needed
JWT Signing Algorithms
Symmetric (HMAC)
- HS256 - HMAC SHA-256
- HS384 - HMAC SHA-384
- HS512 - HMAC SHA-512
Same key for signing and verification
Asymmetric (RSA)
- RS256 - RSA SHA-256
- RS384 - RSA SHA-384
- RS512 - RSA SHA-512
Private key signs, public key verifies
Asymmetric (ECDSA)
- ES256 - ECDSA SHA-256
- ES384 - ECDSA SHA-384
- ES512 - ECDSA SHA-512
Smaller keys, better performance