JWT Token Generator — Create JSON Web Tokens for API Authentication
JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. JWT tokens are widely used for authentication and authorization in modern web applications, APIs, and microservices thanks to their compactness, self-containedness, and digital signing capability.
JWT Token Structure
Header: contains metadata about the token, including the type (always "JWT") and the signing algorithm. Example: {"alg": "HS256", "typ": "JWT"}. The header is Base64URL-encoded and becomes the first part of the token. It may also contain additional fields like "kid" (Key ID) for key identification in multi-key systems.
Payload: contains claims — assertions about the user and additional data. There are three types of claims: registered (standard like iss, exp, sub), public (defined in public registries), and private (custom fields for internal use). The payload is also Base64URL-encoded and becomes the second part of the token.
Signature: created by signing the encoded header and payload using the secret key and the specified algorithm. The signature ensures data integrity and allows verification that the token has not been tampered with. Formula: HMACSHA256(base64UrlEncode(header) + "." + base64UrlEncode(payload), secret).
Signing Algorithms and Their Features
HMAC algorithms (HS256, HS384, HS512): use symmetric encryption with a single secret key for both signing and verification. HS256 is the most popular due to its optimal balance of security and performance. These algorithms are ideal for monolithic applications or systems where all components share one secret key.
RSA algorithms (RS256, RS384, RS512): use asymmetric encryption with a key pair — private for signing and public for verification. This allows distributing the public key for token verification without compromising security. RSA algorithms are ideal for microservice architectures and distributed systems.
ECDSA algorithms (ES256, ES384, ES512): use elliptic curves for asymmetric encryption. They provide the same level of security as RSA but with smaller keys and higher performance. ES256 is becoming the standard for modern high-load systems due to its optimal security-to-speed ratio.
Standard Claims and Their Purpose
Registered claims: "iss" (issuer) indicates who issued the token, "sub" (subject) identifies the token subject (usually a user), "aud" (audience) defines the intended audience, "exp" (expiration time) sets the expiration, "nbf" (not before) indicates when the token becomes valid, "iat" (issued at) records the issuance time, "jti" (JWT ID) ensures token uniqueness.
Custom claims: developers can add custom fields to store user roles, permissions, session identifiers, and other necessary information. It's important to balance functionality and token size, since JWT is transmitted with every request.
JWT Token Security
Secret key protection: the secret key should be sufficiently long (minimum 256 bits for HS256), random, and stored securely. Never include keys in client-side code or public repositories. Use environment variables or specialized key management services.
Token lifetimes: set reasonable lifetimes for different token types. Access tokens typically live 15-30 minutes, refresh tokens — several days or weeks. Short-lived tokens reduce risks in case of compromise but require more frequent renewal.
Token transmission: always use HTTPS for transmitting JWT tokens. Store tokens in secure locations — HttpOnly cookies for web applications, secure storage for mobile apps. Avoid storing in localStorage without additional protection.
Architectural Usage Patterns
Stateless authentication: JWT enables stateless systems where the server doesn't store session information. All necessary information is contained in the token, simplifying scaling and load distribution across servers.
Single Sign-On (SSO): JWT is ideal for implementing SSO, where a user logs in once and gains access to multiple services. The token can contain information about authorized services and access levels.
API Gateway: in microservice architectures, JWT tokens are often used at the API Gateway level for centralized authentication and routing requests to appropriate services based on token information.
Generator Features:
✓ All algorithms supported — HMAC, RSA, and ECDSA algorithms
✓ Flexible settings — full control over header and payload
✓ Secure generation — local processing without sending to a server
✓ Field validation — data correctness checking
✓ Ready templates — quick token creation for typical use cases
✓ Export results — convenient token copying
✓ Educational content — detailed explanations and best practices
Create reliable JWT tokens for your applications following modern security standards and development best practices. Our generator is suitable for both learning and professional development with support for all popular signing algorithms.