JWT Decoder
Decode and inspect JSON Web Tokens. 100% client-side — your tokens never leave your browser.
Related Tools
What is a JSON Web Token (JWT)?
A JSON Web Token (JWT) is a compact, URL-safe token format defined in RFC 7519 for securely transmitting claims between parties. JWTs are widely used for authentication (proving identity), authorization (granting access), and secure information exchange in modern web APIs, mobile apps, and microservice architectures.
JWT Structure (header.payload.signature)
A JWT consists of three Base64URL-encoded parts joined by dots: the header (algorithm and token type, RFC 7515), the payload (claims about the user or session, RFC 7519), and the signature (HMAC or public-key signature over header + payload). The structure is tamper-evident: any modification to header or payload invalidates the signature.
eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0In0.SflKxwRJSMeKKF... └────header───┘ └─────payload─────┘ └────signature─────┘
Why Decode JWTs Client-Side?
JWTs often contain sensitive information — user IDs, email addresses, roles, permissions, or even PII. Pasting a production JWT into a remote decoder leaks all of that to a third-party server, where it may be logged, stored, or analyzed. This tool processes everything in your browser using atob and JSON.parse — the token never leaves your device.
⚠️ Reference Only
Output is generated based on your input and is provided for reference. Results may vary depending on your specific use case, edge cases, or environment-specific behavior. We do not guarantee accuracy of conversions, validations, or computed values.
Always verify critical outputs against official documentation or production environments. We are not responsible for any decisions or losses based on these tool results.
📖 Related Guides
JWT Anatomy — Header, Payload, Signature
Understand JWT structure, claims, and signing algorithms. Security best practices.
URL Encoding — When to Use What
encodeURI vs encodeURIComponent vs escape. Query strings, paths, and reserved characters.
Hash Algorithms — MD5, SHA-1, SHA-256, bcrypt
When to use each hash function. Security comparison and password storage best practices.