Decoded
{
"sub": "1234567890",
"name": "BigDevSoon",
"email": "adrian@bigdevsoon.me",
"role": "admin",
"iat": 1716239022,
"exp": 1716242622
}{
"alg": "HS256",
"typ": "JWT"
}JWT Decoder
SecurityDecode and inspect JSON Web Tokens in real time. View header, payload, claims, and expiration status as you paste.
What is a JSON Web Token?
A JSON Web Token (JWT) is a compact, URL-safe token format used for securely transmitting information between parties. JWTs consist of three Base64URL-encoded parts separated by dots: a header (algorithm and token type), a payload (claims like user ID, roles, and expiration), and a signature that verifies the token has not been tampered with. JWTs are the standard for authentication in modern web applications, API authorization, and single sign-on (SSO) systems.
How to decode and debug JWTs
Decoding a JWT reveals the header and payload without needing the secret key — the data is encoded, not encrypted. This is useful for debugging authentication issues, verifying token claims before making API calls, checking expiration times (exp claim), and understanding what permissions a token grants. This tool decodes both the header and payload, displays all claims in formatted JSON, and highlights the expiration status so you can quickly tell if a token is still valid.
JWT security best practices
Never store sensitive data in JWT payloads since they can be decoded by anyone. Always verify token signatures on the server side. Use short expiration times (15–60 minutes) with refresh tokens for long-lived sessions. Prefer RS256 (asymmetric) over HS256 (symmetric) for public-facing APIs. Store tokens in httpOnly cookies rather than localStorage to prevent XSS attacks. This decoder processes tokens entirely in your browser — no data is sent to any server.
Frequently Asked Questions
Is it safe to paste my JWT here?
Yes. All decoding happens entirely in your browser using JavaScript. No data is sent to any server. However, never share your JWTs publicly — they may contain session information that could be used for unauthorized access until they expire.
Can this tool verify JWT signatures?
This tool decodes and displays the header, payload, and signature parts. It shows the signing algorithm (e.g., HS256, RS256) but does not verify signatures since that requires the secret key or public key, which should never be shared in a browser tool.
What are the most common JWT claims?
Standard claims include: sub (subject/user ID), iat (issued at timestamp), exp (expiration timestamp), iss (issuer), aud (audience), nbf (not before), and jti (unique token ID). Custom claims like roles, permissions, and email are also common.
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