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Security
JWT Decoder
Decode JWT headers, payloads and expiration data.
Header
{
"alg": "HS256",
"typ": "JWT"
}Payload
{
"sub": "1234567890",
"name": "BigForgeKit",
"iat": 1516239022
}Expiration
This token does not contain an expiration claim.
Token security
This tool decodes the token but does not verify its cryptographic signature.
Your JWT is decoded locally in the browser.
About this tool
What is JWT Decoder?
A JWT decoder separates a JSON Web Token into its header and payload so you can inspect algorithms, claims, identifiers and expiration information. BigForgeKit performs this decoding locally and does not send your token to a server.
Features
Built for fast developer workflows
- Decode JWT headers and payloads instantly.
- Display decoded claims as formatted JSON.
- Detect expiration claims and show token status.
- Copy the header or payload independently.
- Process tokens locally without uploading them.
- Clearly distinguish decoding from signature verification.
Frequently asked questions
Questions about JWT Decoder
Does decoding a JWT verify its signature?
No. Decoding only reveals the token header and payload. Signature verification requires the appropriate secret or public key and knowledge of the expected algorithm.
Is it safe to paste a JWT into this tool?
The decoder runs locally in your browser and does not upload the token. Even so, avoid exposing production credentials on untrusted or shared devices.
What does the exp claim mean?
The exp claim contains a Unix timestamp indicating when the token expires. After that time, applications should normally reject the token.
Why can a modified JWT still be decoded?
JWT header and payload sections are encoded, not encrypted. Anyone can decode them. Security comes from verifying the cryptographic signature.
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