JWT Decoder
Decode JWT tokens locally —header, payload, signature. Your token never leaves the browser.
How it works
Paste a token
Copy any JWT and paste it into the box.
Decode
Click Decode. The header and payload are shown as JSON.
Inspect
Review the alg, claims and signature —all decoded locally.
Why use Ercc JWT Decoder?
Privacy
Decoding happens entirely in your browser. Your token is never uploaded.
Clean JSON
Header and payload are pretty-printed for easy reading.
Fast
No signup, no delay. Paste and decode instantly.
Frequently Asked Questions
A JWT has three dot-separated, base64url-encoded parts: the header, the payload, and the signature.
No. Decoding only reads the base64-encoded content. Verifying the signature requires the secret key.
Yes. Everything runs locally in your browser and nothing is sent to any server.
Base64url is base64 with URL-safe characters: + becomes -, / becomes _, and padding is omitted.
Yes, 100% free with no limits. Everything runs locally in your browser.