JWT Decoder for Header and Payload
Inspect JSON Web Token header and payload segments in the browser while debugging authentication examples, claims, and token-shaped data.
Try a safe demo token
Decode only
This tool does not verify signatures, expiration, issuer, audience, or token trust.
Treat decoded claims as untrusted text until your application verifies the token with the expected key, algorithm, issuer, audience, and clock settings.
{
"alg": "HS256",
"typ": "JWT"
}{
"sub": "ascendlab-user",
"name": "AscendLab",
"iat": 1716768000
}A JWT decoder reads the header and payload sections of a JSON Web Token.
Decoding makes claims readable, but it does not prove the token is valid or trusted.
Use development tokens
Avoid pasting sensitive production tokens unless you have a clear local debugging reason.
Treat output as untrusted
Readable claims still need signature, issuer, audience, and expiration validation.
The signature segment is shown only as token text and is not verified.
Use decoded claims for inspection, not for security decisions.
A valid-looking payload does not prove that a token is trusted.
Signature, issuer, audience, expiration, and key rotation must be checked by your application.
Example
Paste a development JWT and inspect claim names before wiring authorization logic.
Assumption
The token uses the common three-part JWT structure with JSON header and payload.
Limitation
This tool does not verify signatures, trust, expiration, issuer, or audience.
Treating decoded claims as trusted
Anyone can edit readable JWT payload data. Trust requires signature, issuer, audience, and expiration checks.
Pasting live user tokens casually
Browser-side decoding still means production tokens may expose sensitive claims on shared devices or screenshots.
Ignoring expiration and audience
A token can look well-formed while being expired, meant for another app, or signed by the wrong issuer.
Claim debugging
Inspect issuer, audience, subject, expiration, scopes, and custom claims.
Auth examples
Decode sample tokens while writing docs, tickets, or test notes.
Header checks
Review algorithm and key ID fields before looking at application validation.
Payload formatting
Copy decoded JSON into a formatter for easier review and comparison.
Decode JWT token
Paste a three-part token and read the header and payload JSON for debugging.
JWT payload viewer
Inspect claims such as iss, sub, aud, exp, scopes, and custom fields without changing the token.
JWT header decoder
Review alg and kid values before checking signature validation in your application.
JWT claims viewer
Copy decoded claims into notes, tickets, or a JSON formatter while keeping trust checks separate.
Is this a JWT validator?
No. It decodes the header and payload only; it does not verify signatures or trust claims.
Can I paste production tokens?
Processing is handled in the browser for this tool, but sensitive production tokens should still be handled carefully.
What claims can I inspect?
You can inspect readable header and payload fields such as alg, kid, iss, sub, aud, exp, scopes, and custom claims.
Why is signature verification excluded?
Verification needs trusted keys plus application-specific issuer, audience, expiration, and key rotation rules.
Suggested workflow
Token inspection path
Decode token-shaped data, format claims, and compare exact payload text during authentication debugging.