JWT Decoder

Encode / Decode

Decode JSON Web Tokens and inspect header, payload, and expiration without a secret.

JWT Token

#jwt decoder#jwt parser#jwt debugger#json web token

About JWT Decoder

Decode JSON Web Tokens and inspect header, payload, and expiration without a secret. JWT Decoder runs entirely in your browser — no installation, no uploads, and no data ever leaves your device.

Common use cases: inspect jwt claims during api debugging; check token expiration without parsing code; audit user roles and permissions encoded in jwts. Whether you are debugging, prototyping, or building production code, having a fast and private tool for this task saves time compared to writing one-off scripts or using an online tool that logs your data.

Like every tool in Catalyst, this one is free forever, requires no login, and is safe to use with confidential data. All processing happens client-side via native browser APIs.

How to use JWT Decoder

1
Open the tool
Open JWT Decoder directly — no signup or installation required. The interactive interface loads instantly.
2
Paste or enter your input
Drop your data into the input area. The tool validates and processes your input live as you type or paste.
3
Review the result
The output updates instantly. If the tool has configuration options, adjust them and watch the result update.
4
Copy or download
Use the copy button to send the result to your clipboard. Nothing is saved between page loads, so closing the tab discards everything.

Frequently asked questions

Does the decoder verify the signature?

No. The decoder parses and displays the header and payload of any JWT without requiring a secret — ideal for inspecting expired, third-party, or debug tokens. For signature verification against a key, use the JWT Builder in the Security Toolkit.

Is it safe to paste a production JWT here?

Yes. The decoder runs 100% in your browser; the token is never transmitted anywhere. That said, JWTs often contain sensitive user IDs and permissions — treat them like passwords and don't share your URL with the token embedded.

What JWT algorithms are supported for decoding?

All algorithms. Decoding only reads the header and payload portions (Base64-URL), which doesn't require knowing the algorithm. HS256, HS384, HS512, RS256, RS384, RS512, ES256, and others are all handled.