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JWT Decoder

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Signature verificationJWT builder

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About JWT Decoder

JWT Decoder parses and decodes JSON Web Tokens so you can inspect their header, payload, and signature without writing any code. It breaks down each segment of the token and displays claims like issuer, expiration, and custom data in a readable format. This tool is essential for backend developers, security engineers, and DevOps professionals working with token-based authentication systems.

Key Features

  • Decodes all three JWT segments: header, payload, and signature
  • Displays registered claims (iss, sub, aud, exp, iat, nbf) with human-readable labels
  • Converts Unix timestamps in exp, iat, and nbf claims to readable date and time formats
  • Highlights expired tokens with a clear visual warning
  • Supports HS256, RS256, ES256, and other common signing algorithms
  • Processes the token entirely in-browser so your secrets never leave your machine

How to Use JWT Decoder

  1. 1

    Paste your JWT

    Copy the full JSON Web Token (the three dot-separated segments) from your authorization header, cookie, or token endpoint response.

  2. 2

    View the decoded header

    The header section shows the signing algorithm (e.g., RS256) and token type, helping you verify the token configuration.

  3. 3

    Inspect the payload claims

    Review all claims in the payload including standard fields like expiration time and any custom claims your application added.

  4. 4

    Check token expiration

    The tool automatically converts the exp claim to a human-readable date and flags whether the token is currently valid or expired.

  5. 5

    Copy individual sections

    Copy the decoded header or payload JSON separately for use in debugging, documentation, or issue reports.

Common Use Cases

Authentication Debugging

Decode access tokens and ID tokens to verify that the correct scopes, roles, and user information are being issued by your identity provider.

Token Expiration Troubleshooting

Quickly check whether a JWT has expired by inspecting the exp claim, which is a common cause of 401 Unauthorized errors in production.

OAuth Flow Verification

Examine tokens received during OAuth 2.0 or OpenID Connect flows to confirm that the issuer, audience, and scopes match your application configuration.

Security Audit

Review JWTs during penetration testing or security reviews to check for weak algorithms (like 'none'), overly long expiration times, or sensitive data in payloads.

Why Use Our JWT Decoder

Instantly decode any JWT and see its header, payload, and expiration status without installing libraries or writing code. Automatic timestamp conversion and expired-token warnings save you from manually converting Unix epochs. Your tokens are decoded entirely in-browser, so sensitive authentication data is never transmitted to an external server.

Your Tokens Never Leave the Browser

JWTs contain sensitive claims including user IDs, roles, email addresses, and expiration data. The JWT Decoder runs entirely in your browser, so production tokens with real user data are never sent to any server. This makes it safe to inspect live tokens without risking exposure or replay attacks.

Frequently Asked Questions

Can this tool verify the JWT signature?
This tool decodes and displays the JWT contents but does not verify the cryptographic signature, as that requires the signing secret or public key. Use your backend library or a dedicated verification tool for signature validation.
Is it safe to paste my JWT into this tool?
Yes. The decoding happens entirely in your browser and no data is sent to any server. However, you should still avoid sharing JWTs publicly since they may contain sensitive claims and could be replayed if not expired.
What does it mean when the algorithm says 'none'?
The 'none' algorithm means the token is unsigned, which is a serious security risk. Legitimate tokens should always use a secure algorithm like RS256 or ES256. If you encounter this in production, investigate immediately.

Last updated: April 6, 2026