JWT Debugger — Free Online Tool

JWT Debugger · Free online tool · 100% offline · No data collection Open in App

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What is JWT Debugger?

JWT Debugger is a free online tool that decodes JSON Web Tokens (JWTs) to inspect their header, payload, and signature. Paste any JWT and instantly see the decoded claims — issuer, subject, expiration time, custom claims — with color-coded sections. Perfect for debugging authentication flows, API integrations, and OAuth implementations. All decoding happens offline in your browser.

How to use JWT Debugger

1 Paste your JWT token into the input field

2 The header (algorithm, type) and payload (claims) decode automatically

3 Review expiration time — the tool highlights expired tokens in red

4 Verify the signature by providing your secret key or public key

Common use cases

Debugging OAuth 2.0 and OpenID Connect authentication flows
Inspecting access tokens during API development
Verifying JWT claims (exp, iat, aud, iss) before processing
Learning how JWT structure works (header.payload.signature)

Frequently Asked Questions

Is it safe to paste my JWT here?

Yes. Decoding happens entirely in your browser. We never see, log, or transmit your tokens. Even signature verification uses your key locally.

What does each JWT section contain?

Header — algorithm (HS256, RS256) and token type. Payload — claims like sub, exp, iat, and custom data. Signature — cryptographic verification that the token hasn't been tampered with.

Can I verify RS256 (public key) signatures?

Yes — paste your public key (PEM format) and the tool verifies the signature cryptographically.

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