Online JWT Generator & Decoder | HS256, HS384, HS512

What is a JWT (JSON Web Token)?

JWT (JSON Web Token) is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. JWTs are digitally signed using a secret (with HMAC algorithms) or a public/private key pair (RSA or ECDSA). Because of their compact size, JWTs can be sent through a URL, POST parameter, or inside an HTTP header. They are self-contained, containing all necessary information about the user, and are secure, as the digital signature verifies authenticity and prevents tampering. They are also stateless, eliminating the need to store session information on the server.

How to Use the JWT Generator and Decoder

Step 1: Select Operation Mode - Choose 'Generate JWT' to create a new token or 'Parse JWT' to analyze an existing one. Each tab provides specific tools for the selected operation.
Step 2: Configure JWT Settings - For generation, select an HMAC algorithm (HS256, HS384, HS512), enter a strong secret key, and define the payload with claims like sub, exp, and iat.
Step 3: Create or Input JWT - To generate, click 'Generate JWT' to create the signed token. To decode, paste an existing JWT into the input field for analysis.
Step 4: Review and Use the Result - Copy the generated token for use in application headers, or view the decoded header and payload information for validation.

Frequently Asked Questions about JWT

What are the common use cases for JWT?

JWTs are widely used for: User Authentication (maintaining session state without server-side storage), API Authorization (protecting REST APIs and microservices), Single Sign-On (SSO), Information Exchange, Mobile App Authentication, and Microservice Communication.

Which JWT algorithms do you support?

Our tool supports the most common HMAC-based JWT signing algorithms: HS256 (HMAC SHA-256), HS384 (HMAC SHA-384), and HS512 (HMAC SHA-512).

What are some JWT security best practices?

Use strong, randomly generated secrets. Always set an appropriate expiration time (exp claim). Never store sensitive information like passwords in the payload. Implement a token refresh mechanism for long-lived sessions. Always validate the JWT signature on the server-side. Use HTTPS to prevent token interception.

What are the standard JWT claims?

Pre-defined claim names for interoperability include: iss (Issuer), sub (Subject), aud (Audience), exp (Expiration Time), nbf (Not Before), iat (Issued At), and jti (JWT ID).

What are common JWT issues and their solutions?

Invalid JSON format in payload: Ensure your payload is valid JSON. Token has expired: Check the 'exp' claim value. Signature verification failed: Verify you are using the correct secret and algorithm. Malformed JWT: A JWT must have three parts separated by dots (header.payload.signature).

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