JWT Decoder
Decodes a JSON Web Token's base64url header and payload for inspection.
Input
Decodes only — it does NOT verify the signature. Never paste tokens containing secrets you don't want decoded locally.
Output
Enter values to see the result.
Runs entirely in your browser. Your input is not uploaded or stored.
How to use this calculator
- Paste a JWT (header.payload.signature).
- Read the decoded header and payload JSON.
How it works
Splits the token and base64url-decodes the header and payload. It does NOT verify the signature.
Worked example
Three parts. A JWT has a header, a payload (claims) and a signature, separated by dots.
Tips
- Runs entirely in your browser. Your input is not uploaded or stored.
Frequently asked questions
Does it check validity?
No — decode only. Don't trust a token's contents without verifying its signature server-side.
Is it safe to paste?
Decoding is local, but avoid pasting production tokens you wouldn't want decoded on this device.
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Cite this tool
Zerdly. (2026). JWT Decoder. Retrieved from https://www.zerdly.com/tools/jwt-decoder/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.