JWT Decoder
Header
Payload
Signature
How to use JWT Decoder
- Paste a JWT (JSON Web Token) string.
- It's split and decoded into its header, payload, and signature sections instantly.
- Inspect the claims (like expiry, subject, or custom fields) without needing a server round-trip.
Limitations
- This decodes and displays the token's contents — it doesn't cryptographically verify the signature against a secret/public key, since that key is something only your backend should hold.
Frequently asked questions
Can I trust the claims shown here?
The decoder shows you exactly what's encoded in the token, which is useful for debugging. It does not verify the signature, so don't treat an unverified token's claims as authenticated — that check has to happen server-side with the signing key.
About this tool
JWT Decoder is a single-purpose utility on instant.tw, a free toolbox of calculators, converters, generators, and quick lookups. Everything works in your browser — nothing is uploaded, nothing is stored on a server unless explicitly noted.
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