JWT Decoder

100% free · Runs 100% in your browser · No signup needed

This tool only decodes the token so you can read it. It does not verify the signature - never trust a token based on this output alone.

Paste your JWT

Header

Payload

Signature & info

Token info will appear here...

Sur JWT Decoder

JWT Decoder - Free Online Tool

The JWT Decoder reads JSON Web Tokens and shows you what is inside - the header, the payload claims, the algorithm, and whether the token has expired. JWTs are the standard for API authentication: after you log in, the server hands you a token, and your app sends it with every request. When something breaks, the first debugging step is always what is actually in this token?

How to use: 1) Paste your JWT (the three-part string separated by dots) into the box. 2) Click Decode Token. 3) Read the pretty-printed header and payload JSON, check the algorithm, and see the expiry status - valid or expired - at a glance.

Why use it: Authentication bugs are among the hardest to diagnose blind. Is the token expired? Does it contain the right user ID and roles? Is the issuer what you expect? Decoding reveals all of this in seconds. Frontend developers use it to verify what their login flow produced; backend developers use it to confirm their token generation is correct before blaming the client.

Key benefits: Instant decoding with beautifully formatted JSON output - no more squinting at base64. Expiry detection with a clear valid/expired badge. Algorithm and token type displayed prominently. Honest security labeling - the tool plainly states the signature is not verified, so nobody mistakes decoding for validation. Fully client-side, which matters because tokens often contain sensitive user data you should not paste into random servers.

FAQs: Does this verify the signature? No - decoding is not verification. A token can decode perfectly and still be forged. Why invalid JWT? Real JWTs have exactly three dot-separated parts; access tokens from some providers are opaque strings, not JWTs. Is it safe to paste my token here? Yes - decoding happens only in your browser, nothing is uploaded. What do exp and iat mean? Expiry time and issued-at time, in Unix seconds.

Pro tips: Always check the exp claim first when debugging 401 errors - expired tokens are the most common cause. Compare the iss (issuer) and aud (audience) claims against your configuration; mismatches here cause silent rejections. Remember that payload contents are only base64-encoded, not encrypted - never put sensitive personal data in a JWT. FistHost also offers a free timestamp converter to read the exp and iat claims as dates.

Related tools: Paste token timestamps into the Timestamp Converter to read expiry as a real date, and hash tokens with the SHA256 Hash Generator when logging them safely. FistHost developer tools are free and private by design.

How to Use JWT Decoder: Step by Step

Paste your JWT (the three Base64 segments separated by dots) into the input field.
The tool instantly splits it into header and payload and displays the decoded JSON claims.
Inspect claims like exp (expiry), iat (issued at), sub (subject), and any custom fields.
Check the expiry timestamp to see whether the token is still valid.
Note: decoding does not verify the signature — verification needs the secret key on your server.

Pro Tips

Never paste production tokens with sensitive claims into sites you don’t trust — this decoder runs in your browser, but stay cautious.
An expired exp claim is the most common cause of “invalid token” errors — check it first.
Keep payloads small; everything in a JWT is readable by anyone who holds it.

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