Auto Decode
Paste a JWT and decode instantly with no extra click. Header and payload update in real time as you edit.
Human Time
Automatically detects iat, exp, and nbf and shows local time with readable status like expired or not yet active.
Local Verify
HS256/384/512 signature verification runs in your browser using WebCrypto. Secrets never leave your device.
What is a JWT decoder?
A JWT decoder splits a token into header, payload, and signature so you can inspect claims and metadata quickly. This tool decodes locally in your browser and keeps your token data private.
How JWT signature verification works
For HMAC-based tokens (HS256, HS384, HS512), verification recomputes HMAC(base64Url(header) + "." + base64Url(payload), secret) and compares it with the token signature.