JWT Generator
JWT Generator FAQ
What is a JWT?
A JWT (JSON Web Token) is a compact, secure way of transmitting information between two parties as a JSON object.
What algorithms are supported?
This tool supports HS256, HS384, and HS512 (HMAC with SHA).
Is this tool secure?
Yes. All JWTs are generated locally in your browser. No data is ever sent to a server.
Can I use these JWTs in production?
This tool is meant for testing and educational use. In production, always use secure libraries and protect your keys properly.
Why do JWTs need a secret?
The secret is used to sign the token, ensuring that nobody can tamper with the payload without invalidating the signature.
What is the structure of a JWT?
A JWT is composed of three parts: Header, Payload, and Signature, separated by dots. Example: `header.payload.signature`.
What is the difference between HS256, HS384, and HS512?
They all use HMAC but with different SHA algorithms (SHA-256, SHA-384, SHA-512). Stronger hashes provide more security but may be slower.
Do JWTs expire?
JWTs can include an `exp` claim in the payload. If present, it defines the expiration time after which the token is invalid.
Can JWTs be revoked?
Not by default, since they are stateless. Revocation typically requires a token blacklist or short expiration times with refresh tokens.
What are common use cases for JWTs?
JWTs are widely used for authentication (Bearer tokens), Single Sign-On (SSO), API access, and secure data exchange.
What is a JWT?
JSON Web Token (JWT) Generator
A JSON Web Token (JWT) is a secure, compact way of representing claims between two parties. JWTs are most commonly used in authentication and authorization systems, where a server issues tokens to clients that can later be verified without requiring traditional session storage.
Structure of a JWT
A JWT is composed of three Base64URL-encoded parts, separated by dots:
xxxxx.yyyyy.zzzzz
- Header — specifies the algorithm (
HS256,HS384,HS512) and the type (JWT). - Payload — contains claims, such as
sub(subject/user ID),iat(issued at),exp(expiration), or custom data like roles. - Signature — generated by hashing
base64UrlEncode(header) + "." + base64UrlEncode(payload)with a secret key. This ensures integrity and authenticity.
Example Breakdown
| Part | Example | Purpose |
|---|---|---|
| Header | {"alg":"HS256","typ":"JWT"} | Defines algorithm and type |
| Payload | {"sub":"123456","admin":true} | User claims (identity, roles, etc.) |
| Signature | HMACSHA256(data, secret) | Validates token integrity |
Why JWTs Are Popular
- Stateless — no server-side session storage needed.
- Compact — small enough for URLs, HTTP headers, or cookies.
- Self-contained — holds all necessary authentication data in one token.
About This Tool
This JWT Generator lets you instantly create tokens using HS256, HS384, or HS512. Everything runs entirely locally in your browser, meaning your payload and secret key never leave your device. This guarantees both privacy and security.
Best Practices
- Always use strong, random secrets for signing tokens.
- Set an expiration (
exp) to limit token lifetime. - Avoid storing sensitive data (like passwords) inside the payload.
- Use HTTPS to protect tokens in transit.
- For high-security systems, prefer asymmetric algorithms like
RS256orES256.
Whether you’re building APIs, Single Sign-On (SSO) systems, or secure communication flows, this tool provides a quick and practical way to test JWT creation while reinforcing proper cryptographic hygiene.