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Decode, inspect, and verify JSON Web Tokens (JWT) instantly.
JSON Web Tokens have become the de facto standard for stateless authentication in modern web applications. Introduced in RFC 7519, JWTs allow servers to issue self-contained tokens that carry identity and authorization information without requiring server-side session storage. This makes them ideal for microservice architectures, single-page applications, and mobile APIs where scalability matters.
Every JWT is composed of three parts separated by periods. The header specifies the signing algorithm (such as HS256 or RS256) and the token type. The payload contains claims - statements about the user and additional metadata. Common claims include sub (subject or user ID), exp (expiration timestamp), iat (issued-at timestamp), and iss (issuer). The signature is created by signing the encoded header and payload with a secret key or private key, ensuring the token has not been tampered with.
Developers frequently need to inspect JWTs during debugging - checking whether a token is expired, verifying the correct claims are present, or confirming the algorithm matches expectations. This tool decodes tokens instantly in your browser, color-codes each section for clarity, and optionally verifies HMAC signatures when you provide the secret key. It supports HS256, HS384, and HS512 algorithms using the Web Crypto API.
Always validate JWTs on the server side - client-side decoding is for inspection only. Use short expiration times and refresh tokens for long-lived sessions. Store tokens in httpOnly cookies rather than localStorage to prevent XSS attacks. Rotate signing keys periodically and never embed sensitive data (like passwords) in the payload, since Base64 encoding is not encryption.
Pro includes JWT validation, signature verification, expiry alerts, and saved token collections.
A JSON Web Token (JWT) is a compact, URL-safe token format used for authentication and information exchange. It consists of three Base64URL-encoded parts separated by dots: the header (algorithm and token type), the payload (claims like user ID, roles, and expiry), and the signature (cryptographic verification).
Yes. This tool runs entirely in your browser using client-side JavaScript. Your token is never sent to any server. However, you should never share JWTs publicly since they may contain sensitive user information, session data, or authorization claims.
This tool supports HMAC-based signature verification including HS256 (HMAC-SHA256), HS384 (HMAC-SHA384), and HS512 (HMAC-SHA512). Enter your secret key to verify the signature. RSA and ECDSA tokens can be decoded but not verified client-side.
Paste your JWT and the tool automatically checks the 'exp' (expiration) claim. It displays whether the token is currently valid or expired, along with the exact expiration date and time in both UTC and your local timezone.
Standard JWT claims include: iss (issuer), sub (subject), aud (audience), exp (expiration time), nbf (not before), iat (issued at), and jti (JWT ID). This tool labels each recognized claim for easy identification.
JWT Decoder is part of BriskTool's collection of free online tools. All processing runs entirely in your browser for maximum privacy and speed.