JWT Decoder — Inspect Tokens Instantly

JWT Decoder — Decode & Inspect JSON Web Tokens

Decode and inspect JSON Web Tokens without needing the secret key. View the header algorithm, all payload claims including user data and expiration time, and verify whether the token has expired. Essential for debugging authentication flows in web and mobile applications.

JWTs consist of three Base64URL-encoded parts separated by dots: the header (specifying the signing algorithm like HS256 or RS256), the payload (containing claims such as sub, iat, exp, and custom data), and the signature (computed from the header and payload using the secret key). This decoder parses the first two parts without requiring the signing key.

Frontend developers inspect JWTs stored in localStorage or cookies to debug login issues. Backend developers verify token claims when troubleshooting authorization failures. API testers examine tokens returned by OAuth flows. Security auditors check what data is exposed in token payloads.

Never store sensitive data like passwords or credit card numbers in JWT payloads — they are encoded, not encrypted, and anyone can decode them. Always check the exp (expiration) claim to verify token validity. For production systems, always validate the signature server-side; decoding alone does not prove authenticity.

Online JWT debuggers like jwt.io offer signature verification if you provide the secret key. This tool focuses on safe inspection without requiring secrets, making it suitable for production token debugging. For generating secure tokens and passwords, see our Password Generator.