JWT Decoder
Paste any JSON Web Token (JWT) and instantly see its decoded header and payload. All processing happens in your browser – 100% private, no data leaves your device.
Important: This tool decodes the token's content only. It does not validate the signature. Always verify JWTs on your backend.
What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe way to securely transmit information between parties as a JSON object. It consists of three parts separated by dots: Header.Payload.Signature. The header typically contains the signing algorithm, the payload contains the claims (user data, expiration, etc.), and the signature verifies the token hasn't been tampered with.
This tool decodes the header and payload – both are Base64Url‑encoded plain JSON. No validation is performed, making it safe for debugging and inspection.
How to Use This JWT Decoder
- 1. Paste your token – Copy the entire JWT (including all three parts) and paste it into the text area above.
- 2. Click "Decode Token" – The tool instantly splits and decodes the header and payload.
- 3. Inspect the data – Review the formatted JSON for algorithm used, claims, and expiration timestamp.
- 4. Copy or export – Use the copy or download buttons to save the decoded data for your records.
Frequently Asked Questions
Is this JWT decoder safe?
Yes – all decoding happens inside your browser. The token never leaves your device, so it's completely safe for sensitive tokens.
Why doesn't the tool check the signature?
Signature verification requires the secret key or public key, which we never ask for. This tool is designed for fast inspection of the token's readable parts – not for cryptographic validation. Always perform validation on your backend.
What can I do with the decoded data?
You can check the algorithm used (`alg`), verify the issuer (`iss`), audience (`aud`), or expiration time (`exp`). This is useful for debugging authentication issues, examining third‑party tokens, or understanding JWT structure.