JWT Decoder

What is a JWT Decoder?

A JWT (JSON Web Token) decoder is a tool that parses and displays the contents of JWT tokens used for authentication and information exchange. JWTs consist of three Base64URL-encoded parts: a header (algorithm and token type), a payload (claims/data), and a signature (verification). Our decoder instantly decodes these parts, displays them in readable JSON format, and extracts standard claims like issuer (iss), subject (sub), audience (aud), expiration time (exp), and more. It also checks expiration status to see if tokens are still valid. Perfect for developers debugging authentication, learning about JWTs, or inspecting token contents.

How to Decode JWT Tokens

Copy your JWT token from your application or authentication flow
Paste the token into the input field (starts with eyJ...)
Click the eye icon to show/hide the token if needed
View the decoded header showing algorithm and token type
Review the payload with all claims and custom data
Check standard claims like issuer, subject, audience
See expiration time and validity status (expired or valid)
Review the signature (Base64URL encoded)
Use the copy buttons to copy header, payload, or signature
Remember: Signature validation requires the secret key

Key Features

Instant Decoding

Decode JWT tokens instantly with real-time parsing and display.

Header Analysis

View algorithm (alg), token type (typ), and other header parameters.

Payload Viewer

Display all payload claims in formatted JSON with syntax highlighting.

Standard Claims

Automatically extract and display iss, sub, aud, exp, nbf, iat, jti claims.

Expiration Check

Automatically check if token is expired and show validity status.

Timestamp Formatting

Convert Unix timestamps to human-readable dates for exp, nbf, and iat.

Copy Functionality

One-click copy for header, payload, or signature.

Show/Hide Token

Toggle token visibility for security when sharing screen.

Error Handling

Clear error messages for invalid tokens or malformed JWTs.

Privacy-First

All decoding happens in browser - token never sent to server.

Common Use Cases

Authentication Debugging

Debug authentication issues by inspecting token contents and expiration.

Learning JWTs

Understand JWT structure and claims by decoding example tokens.

API Development

Verify JWT tokens received from APIs contain expected claims and data.

Token Expiration

Check when authentication tokens expire to troubleshoot session issues.

Security Audits

Inspect JWT tokens for security vulnerabilities or misconfigurations.

Integration Testing

Verify tokens generated by auth systems contain correct information.

Why Choose Our JWT Decoder?

✓Instant decoding with clear, formatted output
✓Automatic extraction of all standard JWT claims
✓Expiration checking with visual validity indicators
✓Human-readable timestamp conversion
✓Show/hide token feature for privacy
✓Copy functionality for header, payload, and signature
✓Detailed error messages for invalid tokens
✓Works with all JWT algorithms (HS256, RS256, etc.)
✓100% client-side - your tokens never leave your browser
✓Clean, easy-to-read interface

Frequently Asked Questions

Is it safe to decode my JWT token here?

Yes! All decoding happens entirely in your browser using JavaScript. Your JWT token is never sent to any server or stored anywhere. However, for production tokens with sensitive data, always exercise caution.

Can this tool verify JWT signatures?

No. Signature verification requires the secret key (for HMAC) or public key (for RSA), which should never be exposed client-side. This tool decodes and displays token contents but does not verify signatures.

What JWT algorithms are supported?

The decoder works with all JWT algorithms (HS256, HS384, HS512, RS256, RS384, RS512, ES256, etc.) because it only decodes the header and payload, not verifies signatures.

What does "exp" mean in the payload?

The "exp" (expiration time) claim indicates when the JWT expires, expressed as a Unix timestamp. Our tool converts this to a readable date and marks expired tokens.

Why can't I decode my token?

JWTs must have exactly 3 parts separated by dots (.). Ensure you've copied the complete token, including all three Base64URL-encoded sections.

What is the difference between iat and exp?

"iat" (issued at) is when the token was created, and "exp" (expiration) is when it expires. The difference between them is the token's validity period.

Can I decode tokens from any authentication system?

Yes! JWTs follow a standard format (RFC 7519), so tokens from any system (Auth0, Firebase, Keycloak, custom auth servers) can be decoded.

What should I do with the decoded information?

Use it to verify your token contains the expected claims, check expiration times, debug authentication issues, or understand the token structure for your application.

About JWT Decoding

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Everything You Need to Know