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JWT Decoder
Paste any JWT and instantly decode the header, payload, and signature – inspect claims, check expiry, and verify token structure without any server call.
✓ Free✓ No signup✓ Privacy first✓ Runs in your browser
JWT Decoder – ToolPremier

Client-side JWT decoding only · never verifies or sends tokens · never share JWTs with untrusted tools

How it works
Convert in three steps

1. Paste your JWT

Drop the full token string into the input field. The three-part structure (header.payload.signature) is detected and split automatically.

2. Inspect the decoded parts

View the decoded header (algorithm, token type) and payload (claims, user data, expiry timestamp) in formatted, readable JSON.

3. Check expiry and claims

See key timestamps converted to readable dates - iat (issued at), exp (expiry), nbf (not before) - so you can tell at a glance whether the token is still valid.

FAQ
Common questions
A JWT (JSON Web Token) is a compact, URL-safe token format used to transmit claims between two parties – most commonly for authentication and session management. It consists of three Base64URL-encoded parts separated by dots: a header (algorithm and token type), a payload (the actual claims – user ID, roles, expiry), and a signature used to verify the token has not been tampered with.
Signature verification requires the secret key (for HMAC algorithms like HS256) or the public key (for RSA/ECDSA algorithms like RS256). This decoder decodes and displays the header and payload without verifying the signature – which is useful for inspection and debugging. For security-critical verification, validate the signature in your application code using your actual secret or public key.
This tool decodes JWTs entirely in your browser – nothing is sent to any server. That said, JWTs from production environments often contain real user data, session tokens, or access credentials. If the token grants access to sensitive systems, treat it like a password: use it only in controlled environments and rotate it after testing if there’s any chance it was exposed.
Standard registered claims include: iss (issuer – who created the token), sub (subject – who the token is about), aud (audience – who should receive it), exp (expiration time), iat (issued at time), and jti (JWT ID for uniqueness). Of these, exp and iat are the most practically important – always verify expiry in your application logic.
Keep going
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About the JWT Decoder
JWTs are everywhere in modern web development – OAuth flows, API authentication, microservice communication, and session management all use them. Debugging a JWT issue usually means needing to read what’s actually inside the token: which claims are present, what the expiry timestamp says, whether the algorithm matches what your server expects. This decoder splits the three-part token structure, Base64URL-decodes each segment, and presents the header and payload as formatted JSON with timestamps converted to readable dates. It runs entirely in your browser – your token is never sent anywhere, which matters when you’re debugging tokens from staging or production environments.
Benefits
  • Decodes header and payload into formatted, readable JSON immediately.
  • Converts exp, iat, and nbf Unix timestamps to human-readable dates.
  • Flags token structure issues - malformed or non-JWT strings are flagged clearly.
  • Fully client-side - tokens never leave your browser, safe for use with sensitive tokens.
Privacy
JWT decoding runs entirely in your browser. Token contents are never transmitted to, stored on, or processed by any server.