JWT Decoder & Debugger

Decode JSON Web Tokens locally in real-time. Inspect claims, verify expiration timestamps, and analyze algorithm headers without transmitting secrets.

Sample Tokens:

Encoded Token (Base64URL):

Awaiting Token

Header: Algorithm & Token Type ALG: -

Payload: Data Claims & Expiration EXP: -

Verify Signature: Cryptographic Hash

Parsed Claims Breakdown:

Claim Key	Standard Meaning	Decoded Value
No claims parsed yet.

What is a JSON Web Token (JWT)?

A JSON Web Token (JWT) (RFC 7519) is a compact, URL-safe standard for transferring claim assertions between two parties. JWTs consist of three distinct parts separated by dots (.):

1. Header

Contains metadata specifying the signature algorithm (e.g., HS256, RS256) and token type.

2. Payload

Holds the claims (user identities, roles, permissions, issued timestamps, and expiration times).

3. Signature

Verifies that the sender is authentic and ensures the token contents were not tampered with.

Registered JWT Claims Glossary

Claim	Full Name	Description
`iss`	Issuer	Identifies the principal/authorization server that issued the token.
`sub`	Subject	Identifies the user or system principal represented by the token.
`aud`	Audience	Specifies the intended recipients or target API service.
`exp`	Expiration Time	Unix timestamp after which the token must be rejected.
`nbf`	Not Before	Unix timestamp specifying when the token becomes valid.
`iat`	Issued At	Unix timestamp recording when the token was generated.

How to use JWT Decoder & Debugger

Enter or paste the values requested in the input fields.
Choose any options provided, then run an action button if the tool requires one.
Review the result and copy or adjust it as needed.

JWT Decoder & Debugger features

Available tool controls: Standard Auth Token, Expired Token.
Input and option fields: Encoded Token (Base64URL):, Header: Algorithm & Token Type, Payload: Data Claims & Expiration.

Using JWT Decoder & Debugger in a development workflow

Use a controlled sample and identify exactly what the tool verifies or generates. Do not treat decoding as authentication, or a generated value as a complete security policy. Check algorithms, key sizes, expiry, and application-specific requirements before relying on the result.

Use safe test data for this check

Try a non-sensitive example first, then confirm the selected algorithm or policy matches the system you are working with.
Pay attention to these page fields: Encoded Token (Base64URL):, Header: Algorithm & Token Type, Payload: Data Claims & Expiration. Confirm which fields are inputs, options, or output areas before processing.
The page exposes these relevant actions: Standard Auth Token, Expired Token. Choose only the action that matches the result you need.
Do not treat a visual result as proof that an application is secure. Confirm the relevant algorithm, deployment settings, and threat model in the system that will use it.

Limits to keep in mind before deployment

Use non-production examples where possible. Decoding or generating a value does not by itself verify a signature, secure an application, or replace a security review.

Frequently Asked Questions (FAQ)

No. Standard JWS (JSON Web Signature) tokens are signed, not encrypted. Their payload values are merely Base64URL-encoded and can be read by anyone who holds the token string. Never store sensitive credentials (like database passwords or API keys) in a standard JWT payload.

No. All parsing, Base64URL decoding, and timestamp calculations execute strictly inside your browser environment using client-side JavaScript.

The exp claim uses standard NumericDate representation (seconds since January 1, 1970 UTC). The decoder converts this integer into your local system time zone to display human-readable expiration status.