Generate & Sign Custom JWT Tokens
Create secure JSON Web Tokens for testing and development. Define custom claims, choose signing algorithms, and generate signed JWTs instantly with our free generator. Perfect for mocking authentication in APIs and web apps.
How the JWT Generator and Signer Works
This tool creates signed JSON Web Tokens from custom header and payload claims. You define the token contents, select a signing algorithm, provide a secret key, and get a ready-to-use JWT.
Token Creation Process
- Configure the header - select algorithm (HS256, HS384, HS512, or none)
- Add payload claims - standard claims (sub, name, iat) are pre-filled
- Add custom claims by entering a key-value pair and clicking "Add"
- Enter your secret key for signing (not needed for "none" algorithm)
- Click "Generate JWT" to create the signed token
- Copy the generated token for use in Authorization headers or cookies
Specific Use Cases
API Testing with Custom Tokens
A QA engineer needs to test API endpoints with different user roles. They generate tokens with custom "role" and "permissions" claims to verify access control works correctly.
Prototyping Authentication Flows
A frontend developer building a demo needs valid JWTs without setting up a full auth backend. They generate tokens with realistic claims to test token handling in their application.
Creating Service-to-Service Tokens
A backend engineer sets up inter-service authentication. They generate tokens with "iss" (issuer) and "aud" (audience) claims to ensure tokens are only accepted by intended services.
Testing Token Expiration Handling
A developer tests how their app handles expired tokens. They manually set the "exp" claim to a past timestamp and verify the application correctly rejects the token.
Generating Tokens for Documentation Examples
A technical writer creates API documentation with realistic JWT examples. They generate properly signed tokens that readers can decode to understand the claim structure.
What to Know Before Using This Tool
Important details about JWT generation and signing:
- Supports HS256, HS384, HS512 (HMAC-SHA) algorithms for signing
- The "none" algorithm creates unsigned tokens - useful for testing only
- Standard claims like "iat" (issued at) are auto-populated with current timestamp
- Custom claims can be any string key with string values
- The "sub" claim typically holds the user ID or subject identifier
- Tokens are base64url-encoded and ready for Authorization: Bearer headers
- Generated tokens are valid until the "exp" claim time (if set)
Frequently Asked Questions
What claims should I include in a JWT?
Common claims: "sub" (subject/user ID), "iat" (issued at), "exp" (expiration). Optional: "name", "email", "role", "permissions". Avoid sensitive data like passwords.
How do I set token expiration?
Add an "exp" claim with a Unix timestamp (seconds since 1970). For example, for 1-hour expiration, set exp to current time + 3600 seconds. The tool auto-fills "iat" but you must set "exp" manually.
What's the difference between HS256, HS384, and HS512?
They use different SHA hash lengths: 256, 384, and 512 bits respectively. HS256 is secure for most uses. HS384 and HS512 provide higher security margins but produce slightly larger signatures.
Can I create tokens that work with my production system?
Yes, if you use the same secret key and algorithm as your production system. However, be careful - tokens created this way are valid credentials. Only do this in secure development environments.
What does the "typ" header field mean?
"typ" stands for "type" and is typically set to "JWT". It identifies the token format. This is a standard header field along with "alg" (algorithm).
Why would I use the "none" algorithm?
The "none" algorithm creates unsigned tokens - anyone can verify them without a secret. This is only for testing and development. Never use "none" in production as tokens can be forged.
How do I add numeric or boolean claims?
This tool currently supports string values for custom claims. For numeric or boolean claims, you'll need to modify the token payload directly or use a more advanced JWT editor.
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