AUTH DEBUG

JWT Decoder

> Decode JWT header and payload locally in your browser.
> Inspect exp, iat, and nbf claims without sending bearer tokens to third-party sites.

JWT or Bearer token

Decode only

This tool decodes header and payload locally. It does not verify the signature or prove the token is trustworthy.

Header JSON

// Decoded JSON appears here...

Payload JSON

// Decoded JSON appears here...

Claim timing

Header, payload, signature segment state, and timestamp analysis will appear here.

Signature segment

// Signature segment appears here...

What this tool can and cannot tell you

Can decode header/payload structure locally.
Can show readable timestamps for exp, iat, and nbf.
Cannot verify the cryptographic signature.
Cannot prove the token was issued by the expected system.

FAQ

Does JWT Decoder send my data anywhere?↓

No. JWT Decoder runs entirely in your browser using built-in JavaScript APIs. Your input never leaves the device, never touches our servers, and never reaches third-party APIs. Tokens, customer data, and proprietary payloads stay private — paste freely without worrying about leaks.

What happens to invalid or malformed input?↓

The tool validates input and reports precise errors with the offending position rather than failing silently. Common issues like truncated data, wrong encoding, or malformed syntax are flagged before the operation so you can fix the input rather than chase a downstream bug in production.

Are there size limits?↓

There is no hard cap. The practical limit is browser memory — most modern devices handle multi-megabyte payloads without trouble. Very large files (50+ MB) may take a few seconds to process. The tool stays responsive via incremental rendering and never freezes the page on large inputs.

Is JWT Decoder free for commercial use?↓

Yes. No account, no usage quota, no advertising on results, no licensing fee. Use it freely in personal projects, internal tooling, and client work. The conversion logic is browser-visible — no hidden remote calls, no tracking on inputs, no terms that restrict commercial output.

Popular Use Cases

Explore the most common scenarios for JWT Decoder below. Each page is a focused calculator with worked examples and edge-case guidance.

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Header JSON

Payload JSON

Signature segment

JWT Decoder

Header JSON

Payload JSON

Claim timing

Signature segment

What this tool can and cannot tell you

FAQ

Popular Use Cases

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