JWT Decoder

Decode and inspect JSON Web Tokens with detailed analysis

JWT Token

JWT Decoder

Token Information

Token Length:0 characters

Parts:0/3

Format:Invalid Format

What is a JWT Decoder?

A JWT Decoder (JSON Web Token Decoder) is a specialized tool that helps developers, QA engineers, and security professionals decode and inspect JSON Web Tokens. JWTs are widely used for authentication, authorization, and secure data transmission in modern web applications, APIs, and microservices.

Our free JWT Decoder allows you to instantly decode JWT tokens into their component parts—header, payload, and signature— making it easy to inspect claims, verify token structure, and debug authentication issues. No installation required, and all processing happens securely in your browser.

Understanding JSON Web Tokens (JWT)

A JSON Web Token (JWT) is a compact, self-contained way of transmitting information between parties as a JSON object. JWTs consist of three parts separated by dots (.) and are Base64URL encoded:

header.payload.signature

Header: Contains the token type (JWT) and signing algorithm (e.g., HS256, RS256, ES256)
Payload: Contains claims—statements about the entity and additional data. Includes standard claims like exp (expiration), iat (issued at), sub (subject)
Signature: A cryptographic signature created by encoding the header and payload with a secret or private key

Key Features of Our JWT Decoder

✓ Instant Decoding

Paste any JWT token and instantly see the decoded header, payload, and signature components.

✓ View All Claims

Inspect all claims in the JWT payload including user ID, roles, permissions, expiration time, and custom claims.

✓ Algorithm Support

Supports all major signing algorithms: HS256, HS384, HS512, RS256, RS384, RS512, ES256, ES384, ES512, and more.

✓ Signature Verification

Optionally verify JWT signatures if you have access to the signing secret or public key.

✓ JSON Pretty Print

Decoded payloads and headers are automatically formatted for easy reading and inspection.

✓ No Installation Required

100% free online tool. No download, registration, or plugins needed. Works on all modern browsers.

Common Use Cases for JWT Decoder

Authentication Debugging: Inspect JWT tokens to verify user information and claims in authentication flows.
API Testing: Decode tokens returned by OAuth 2.0 and OpenID Connect providers during API testing.
QA & Testing: Validate JWT structure and claims in test payloads and authorization headers.
Troubleshooting: Identify why authentication is failing by examining token contents and expiration times.
Token Validation: Verify that tokens contain expected claims before processing API requests.
Security Review: Audit what information is being stored in JWT tokens, especially sensitive data.
Development & Debugging: Inspect OAuth tokens, ID tokens, and access tokens during development.
Microservices Communication: Validate JWT tokens passed between microservices for proper authorization checks.

Why Use Our JWT Decoder?

✓ 100% Secure: All processing happens locally in your browser—no token is sent to any server
✓ 100% Free: No subscriptions, no licensing, no hidden costs
✓ Fast & Instant: Decode tokens immediately with no delays
✓ Works Offline: Use the tool without internet connection after first load
✓ Mobile Friendly: Responsive design works on desktop, tablet, and mobile devices
✓ Supports All Algorithms: HS256, RS256, ES256, and many more
✓ Developer Trusted: Used by developers and QA teams worldwide for JWT debugging
✓ Read Token Details: View all claims, expiration times, and custom data in tokens

How to Use the JWT Decoder

Copy Your JWT Token: Get the JWT token from your browser's Network tab, authorization header, or response body
Paste the Token: Paste the complete JWT (including header.payload.signature) into the input field
View Decoded Content: The decoder instantly displays the decoded header and payload in JSON format
Inspect Claims: Review all claims in the payload including expiration time, issuer, subject, and custom claims
Verify Signature: Optionally verify the signature if you have the secret key or public key available
Copy Results: Copy decoded content to clipboard for documentation or further analysis

JWT Best Practices & Tips

Common JWT Claims:

iss (Issuer): Identifies who issued the token
sub (Subject): Identifies the principal that is the subject of the JWT (usually user ID)
aud (Audience): Identifies the recipients the JWT is intended for
exp (Expiration Time): Specifies when the token expires (in Unix timestamp)
iat (Issued At): Specifies when the token was issued
nbf (Not Before): Specifies when the token becomes valid
jti (JWT ID): Unique identifier for the token

Security Best Practices:

Never store sensitive information in JWT payloads—they are encoded but not encrypted
Always validate JWT signatures to ensure tokens haven't been tampered with
Check token expiration time (exp claim) before processing
Use HTTPS to transmit tokens to prevent interception
Store tokens securely in httpOnly cookies or secure storage
Use strong, randomly generated secrets for HS256 signing
Regularly rotate signing keys and revoke compromised tokens
Implement token refresh mechanisms for long-lived sessions
Verify audience (aud) and issuer (iss) claims match your application

When to Use JWT Decoder:

Debugging authentication failures in your application
Verifying that OAuth providers return correct token data
Checking JWT expiration times when tokens are rejected
Inspecting custom claims in microservices communication
Auditing what user data is being transmitted in tokens
Testing API endpoints that require JWT authorization
Learning how JWT structure and claims work

Frequently Asked Questions About JWT Decoder

Q: Is my JWT token stored or shared when I decode it?

No. All decoding happens entirely in your browser. Your JWT token is never sent to any server—it remains completely private and secure.

Q: Can the decoder verify JWT signatures?

Yes! If you have the secret key (for HS256, HS384, HS512) or public key (for RS256, ES256, etc.), you can verify that the JWT signature is valid and hasn't been tampered with.

Q: What's the difference between HS256 and RS256?

HS256 (HMAC) is symmetric encryption—the same secret is used for signing and verification. RS256 (RSA) is asymmetric—a private key signs tokens, and a public key verifies them. RS256 is generally more secure for multi-party systems.

Q: Can I decode an expired JWT?

Yes! The decoder will show you all the token's contents including the expiration time (exp claim). However, expired tokens should not be used for authorization.

Q: What does the "invalid signature" message mean?

It means the token's signature doesn't match the content. This could happen if the token was tampered with or signed with a different secret than what you're using to verify.

Q: Can I use this tool to forge JWTs?

This tool is for decoding and inspecting JWTs. To create or sign JWTs, you need authentication libraries in your programming language. Never forge tokens—it's a security risk!

Q: What if I see claims I don't recognize in the payload?

JWTs can contain standard claims (iss, exp, aud) and custom claims. Custom claims are specific to your application. Review your application's documentation to understand what custom claims should be present.

Q: Can the decoder handle JWTs with very long payloads?

Yes! The tool handles JWTs of various sizes. Paste the complete token, and it will decode and display all the contents regardless of payload size.

Q: How do I get a JWT token to test?

You can get JWTs from: OAuth 2.0 providers like Google or GitHub, your application's login response, authorization headers in browser Network tabs, or by generating test tokens using JWT libraries.

JWT Decoder for QA & API Testing

For quality assurance professionals and API testers, JWT decoders are essential tools for validating authentication and authorization flows. Here's how QA teams use JWT decoders:

Auth Flow Testing: Validate that login endpoints return correctly formatted JWTs with expected claims
Token Expiration Testing: Verify that expired tokens are rejected and new tokens are issued correctly
Permission Testing: Check that JWT claims correctly represent user roles and permissions
OAuth Testing: Inspect ID tokens and access tokens from OAuth providers
API Authorization: Verify that API endpoints properly validate JWT tokens in Authorization headers
Microservices Testing: Validate JWT propagation across microservices for proper authorization

Our JWT Decoder is specifically designed for developers and QA teams testing authentication systems, providing instant insights into token structure, claims, and expiration times to help you verify security configurations are working correctly.

Start Decoding Your JWT Tokens Today

Whether you're a developer debugging authentication issues, a QA engineer testing OAuth flows, or a security professional auditing token usage, our free JWT Decoder is the fastest way to inspect and understand JWT tokens. No installation required, no tokens stored on servers—just instant, secure decoding in your browser. Try it now and streamline your JWT debugging and testing!

JWT Decoder

JWT Token

Token Information

What is a JWT Decoder?

Understanding JSON Web Tokens (JWT)

Key Features of Our JWT Decoder

✓ Instant Decoding

✓ View All Claims

✓ Algorithm Support

✓ Signature Verification

✓ JSON Pretty Print

✓ No Installation Required

Common Use Cases for JWT Decoder

Why Use Our JWT Decoder?

How to Use the JWT Decoder

JWT Best Practices & Tips

Common JWT Claims:

Security Best Practices:

When to Use JWT Decoder:

Frequently Asked Questions About JWT Decoder

Q: Is my JWT token stored or shared when I decode it?

Q: Can the decoder verify JWT signatures?

Q: What's the difference between HS256 and RS256?

Q: Can I decode an expired JWT?

Q: What does the "invalid signature" message mean?

Q: Can I use this tool to forge JWTs?

Q: What if I see claims I don't recognize in the payload?

Q: Can the decoder handle JWTs with very long payloads?

Q: How do I get a JWT token to test?

JWT Decoder for QA & API Testing

Start Decoding Your JWT Tokens Today

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