JWT Decoder Online - Free JSON Web Token Parser

Decode and inspect JWT tokens. Fast, secure, and completely free. All processing happens in your browser — no data is sent to any server.

What is a JWT Decoder?

A JWT Decoder splits a JSON Web Token into its three dot-separated segments — header, payload, and signature — and Base64URL-decodes the first two into readable JSON, so you can inspect claims like exp (expiration), iss (issuer), sub (subject), and any custom claims your application adds. Decoding is purely a read operation: it does not check whether the signature is valid, so a decoded token that looks legitimate could still be forged, expired, or issued by the wrong authority. For that, you need actual signature verification, which this tool intentionally does not perform.

How to Use JWT Decoder

1. Paste a JWT (the full string with two dots separating three segments) into the input field
2. The header and payload are decoded and displayed as formatted JSON automatically
3. Check the exp, iat, and nbf timestamp claims to understand the token's validity window
4. Review custom claims your application relies on (roles, permissions, tenant IDs, etc.)
5. Use the JWT Validator separately when you need to verify the signature, not just read the claims

Key Features

• Decodes and formats both the header and payload as readable JSON
• Converts standard timestamp claims (exp, iat, nbf) into human-readable dates
• Clearly separates the three JWT segments (header, payload, signature)
• Handles both standard and URL-safe Base64URL encoding used by JWTs
• Decoding happens entirely client-side — safe for tokens containing sensitive claims

Why Use JWT Decoder?

When an API call fails with a 401 and you have a JWT in hand, the fastest way to understand why is usually to look inside it: has the token actually expired, does it have the audience the API expects, is it even the token you thought you were sending? Decoding it instantly answers those questions without writing a script or trusting a third-party tool with a token that might carry sensitive claims — everything happens locally in your browser.

Common Use Cases

• Debugging a 401 Unauthorized error by inspecting a token's expiration and audience claims
• Checking what roles or permissions are embedded in an access token
• Verifying that a token issuer (iss) matches the expected identity provider
• Inspecting custom claims added by your own authentication service
• Comparing two tokens side by side to spot a configuration difference

Frequently Asked Questions

Does decoding verify that the JWT's signature is valid?

No — decoding only reads and displays the header and payload; it doesn't check the signature at all. A token could be completely fabricated and still decode successfully. Use the JWT Validator to actually verify signatures.

Is it safe to paste a production access token into this tool?

Decoding runs entirely in your browser with no data sent to a server, so it's technically safe from a network perspective — but treat any real token carefully and avoid sharing screenshots of decoded output that reveal sensitive claims.

What does the exp claim actually mean?

exp is a Unix timestamp marking when the token expires; once the current time passes that value, a properly implemented API should reject the token regardless of whether the signature is still valid.

Why do I see three sections when I decode a JWT?

A JWT always has three dot-separated parts: the header (algorithm and token type), the payload (the actual claims), and the signature (used to verify the first two haven't been tampered with).

Can I decode a malformed or truncated JWT?

If a segment is missing or not valid Base64URL/JSON, decoding that segment will fail and the tool will indicate which part couldn't be parsed, which itself is often useful for spotting where a token got corrupted.

Guides

• API Authentication Methods: API Keys, JWT, OAuth 2.0 Explained

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