JWT Token Generator
Generate and decode JSON Web Tokens (JWT) for secure authentication and data exchange. This tool supports HS256, HS384, and HS512 algorithms with a customizable payload and expiry time.
JWT Token Generator
Generate and decode JSON Web Tokens (JWT) with HS256, HS384, and HS512 algorithms.
JWT Tips
- What is JWT? JSON Web Token (JWT) is a compact, URL-safe token format for secure data exchange.
- Structure: JWT consists of three parts: Header, Payload, and Signature, separated by dots (.).
- Use Cases: Authentication, authorization, and information exchange.
- Security: Always use strong secrets and HTTPS to protect tokens.
- Expiry: Always set an expiration time (exp) to limit token validity.
How to Use the JWT Token Generator
Enter Payload Data
Enter your JSON payload data or use one of the example templates (User, API, Payment).
Set Secret & Algorithm
Enter a secret key (min 8 characters) and select the signing algorithm (HS256, HS384, or HS512).
Generate & Copy Token
Click Generate Token and copy the generated JWT for use in your application.
What Is a JWT (JSON Web Token)?
A JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. This information can be verified and trusted because it is digitally signed. JWTs are commonly used for authentication and authorization in web applications, APIs, and microservices. Unlike session-based authentication, JWTs are stateless—the server doesn't need to store session data, making them ideal for distributed systems.
Why Use JWT Tokens?
JWT tokens offer significant advantages for modern applications. They're stateless, meaning servers don't need to store session information. They're compact and URL-safe, making them easy to transmit. They can carry user information directly in the token. They work seamlessly across different domains and services. They support expiration and other security claims. For APIs, single-page applications, and mobile apps, JWT has become the standard authentication mechanism.
Key Features
- Token Generation: Create JWTs with custom payloads and HS256, HS384, or HS512 algorithms.
- Token Decoding: Decode existing JWTs to inspect header and payload contents.
- Signature Verification: Verify token signatures using your secret key.
- Example Templates: Pre-built payload templates for common use cases (User, API, Payment).
- Strong Secret Generator: Generate cryptographically strong secret keys.
- Expiry Configuration: Set token expiration times from 60 seconds to 24 hours.
- Expiration Detection: Automatically detect and warn about expired tokens.
- Instant Processing: Generate and decode tokens immediately.
JWT Structure Explained
Header
The header typically contains the token type (JWT) and the signing algorithm (HS256, HS384, or HS512). Example: {"alg":"HS256","typ":"JWT"}
Payload
The payload contains claims—statements about the user and additional metadata. Standard claims include iss (issuer), exp (expiration), sub (subject), and iat (issued at). Custom claims can include user IDs, roles, and permissions.
Signature
The signature verifies that the token hasn't been tampered with. It's created by signing the encoded header and payload with a secret key using the specified algorithm.
Supported Algorithms
HS256 (HMAC SHA-256)
Uses SHA-256 with a shared secret. Widely supported and recommended for most applications.
HS384 (HMAC SHA-384)
Uses SHA-384 for stronger security. Slightly larger tokens than HS256.
HS512 (HMAC SHA-512)
Uses SHA-512 for maximum HMAC security. Largest tokens but strongest signature.
Common Use Cases
API Authentication
Issue JWTs to authenticated users. Clients include the token in request headers for subsequent API calls.
Single Sign-On (SSO)
Share JWTs across multiple applications for seamless authentication.
Mobile App Authentication
Use JWTs for stateless authentication in mobile applications.
Microservices
Pass JWTs between microservices to maintain authentication context.
Information Exchange
Securely transmit information between parties with signature verification.
JWT Security Best Practices
Always use strong, random secret keys (minimum 32 characters for HS256). Set appropriate expiration times—shorter for sensitive operations. Use HTTPS to prevent token interception. Never store sensitive data in the payload—it's only encoded, not encrypted. Validate all claims (iss, aud, exp) when verifying tokens. Implement token refresh mechanisms for long-lived sessions. Consider using RS256 (asymmetric) for multi-party scenarios.
Frequently Asked Questions
Is JWT encrypted?
No, standard JWTs are signed but not encrypted. The payload is Base64-encoded and readable by anyone. Never put sensitive data in a JWT payload.
How long should a JWT last?
Short-lived tokens (15 minutes to 1 hour) are more secure. Use refresh tokens for longer sessions.
What's the difference between HS256 and RS256?
HS256 uses a shared secret for signing and verification. RS256 uses a private key for signing and a public key for verification, useful when multiple parties need to verify tokens.
Can I decode a JWT without the secret?
Yes, the header and payload are Base64-encoded and can be decoded without the secret. The signature cannot be verified without the secret.
Is the tool free?
Yes, ZourTools JWT Token Generator is completely free, with no limitations.