JWT Decoder
Our JWT Decoder helps developers quickly inspect and debug JSON Web Tokens. Perfect for understanding token structure, verifying claims, and troubleshooting authentication issues in modern web applications.
How to Use This Calculator
Paste your JWT token into the input field (JWTs typically start with "eyJ" and have three parts separated by dots). Click "Decode JWT" to parse and display the token's header and payload in formatted JSON. The header shows the token type and signing algorithm (like HS256 or RS256), while the payload contains claims like user data, permissions, and expiration times. Use this to analyze token structure, verify claims, check expiration, or debug authentication issues. This tool only decodes—it doesn't verify the signature.
Why JWT Tokens Matter
JWTs are the industry standard for stateless authentication in modern web applications. They eliminate server-side session storage, making them ideal for scalable, distributed systems, RESTful APIs, and microservices. Major platforms like Google, Microsoft, and Auth0 use JWTs for OAuth 2.0 and OpenID Connect. JWTs contain user information and permissions in a compact, URL-safe format that can be verified cryptographically. Understanding JWT structure is crucial for developers building secure authentication systems, debugging auth flows, and ensuring proper security implementation in cloud-native applications.
Frequently Asked Questions
Can this tool verify if a JWT is valid?
No. This tool only decodes tokens to show contents. Verifying requires the secret or public key used to sign it, which must be kept secure on the server. Always verify tokens server-side using proper JWT libraries.
What information is stored in a JWT?
JWTs typically contain user identification, permissions or roles, expiration time (exp), issued at time (iat), and custom claims. The exact contents depend on what the authentication server includes when creating the token.
Is it safe to decode JWTs?
Yes. Decoding is safe—header and payload are Base64-encoded, not encrypted. However, never share JWT tokens publicly as they may contain sensitive information. Security comes from the signature, which prevents tampering.
Is my JWT token sent to a server?
No. All decoding happens in your browser. Your JWT token never leaves your device, ensuring complete privacy and security for sensitive information.