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Local-Only

Online JWT Decoder & Inspector

Paste any JSON Web Token to instantly decode and inspect its header, payload, and registered claims. Standard claims like expiration (exp), issued-at (iat), and subject (sub) are automatically parsed into human-readable formats.

This is a local-only decoder — your token never leaves your browser. Important: decoding a JWT reveals its contents but does not verify its cryptographic signature.

Your token is decoded 100% locally in your browser. It is never logged or sent to any server.
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How It Works (Step-by-Step)

1

1. Paste Your Token

Copy a JWT from your application, API response, or authentication header and paste it into the input field.

2

2. View Decoded Sections

The header and payload are instantly decoded and displayed as formatted JSON. Timestamp claims are converted to readable dates.

3

3. Inspect Claims

Review the algorithm, token type, expiration status, issuer, audience, and other registered claims at a glance.

Key Features & Advantages

Instant Local Decoding

Decodes JWTs entirely in your browser using standard Base64URL parsing. No server requests, no token logging, no external API calls.

Human-Readable Claims

Automatically converts Unix timestamps in exp, iat, and nbf claims to readable date and time formats. Highlights whether the token is currently expired.

Structured Header & Payload

Displays the decoded header (algorithm, token type) and payload (all claims) as properly formatted, syntax-highlighted JSON.

Malformed Token Handling

Gracefully handles truncated, corrupted, or non-JWT input with clear error messages instead of cryptic failures.

Security-First Design

Prominently warns that decoding does not equal verification. Never validates signatures, never suggests that decoded tokens are trusted.

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Frequently Asked Questions

What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe token format used to transmit claims between two parties. It consists of three Base64URL-encoded parts separated by dots: a header (algorithm and type), a payload (claims data), and a signature.
Is decoding a JWT the same as verifying it?
No. Decoding simply reveals the contents of the header and payload by reversing the Base64URL encoding. Verification requires checking the cryptographic signature using the appropriate secret key or public key. This tool only decodes — it does not verify signatures.
Can a JWT be decoded without a secret key?
Yes. The header and payload of a JWT are only Base64URL-encoded, not encrypted. Anyone with access to a JWT can decode and read its contents. This is by design — JWTs are meant to carry claims that can be read, while the signature ensures they have not been tampered with.
Is it safe to paste a JWT into this tool?
Yes. This decoder processes your token entirely inside your browser. The token is never sent to a server, logged, or stored. However, you should always be cautious about pasting production tokens into any online tool — this tool is designed to be a safe exception because it is fully client-side.
What JWT claims does this tool decode?
This tool decodes all claims in the payload, including standard registered claims like iss (issuer), sub (subject), aud (audience), exp (expiration), iat (issued at), nbf (not before), and jti (JWT ID). Custom claims added by your application are also displayed.

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