JWT Decoder

Decode, verify, and edit JSON Web Tokens

Load sample:

JWT Token

How to Use This Tool

Choose Mode

Select 'Decode Token' to analyze existing JWTs or 'Create Token' to build new ones.

Decode JWT Tokens

Paste any JWT token to see its header, payload, and signature. The tool validates expiration and structure.

Create JWT Tokens

Edit the header and payload JSON to create custom tokens. Use quick actions to set timestamps.

Understand Token Status

Color-coded indicators show if tokens are valid, expired, or not yet valid based on time claims.

Copy Decoded Data

Extract individual sections (header, payload) or copy the entire decoded JSON for further use.

Pro Tips

•JWT tokens consist of three parts separated by dots: header.payload.signature
•Time-based claims (iat, exp, nbf) use Unix timestamps (seconds since epoch)
•The tool shows human-readable dates for all timestamp claims
•Created tokens are unsigned (alg: none) - for production, use proper signing
•Standard claims like 'iss' (issuer) and 'sub' (subject) have special meanings
•Load sample tokens to see examples of different JWT structures and claims

What is a JWT Decoder?

A JWT (JSON Web Token) decoder is a tool that parses and validates JSON Web Tokens, revealing their structure and content. JWTs are compact, URL-safe tokens used for securely transmitting information between parties as a JSON object. Our JWT decoder not only decodes tokens but also validates their structure, checks expiration times, and allows you to create new tokens for testing. Understanding JWT structure is crucial for implementing secure authentication and authorization in modern web applications.

Key Features

Decode any JWT token to view header, payload, and signature

Real-time token validation with expiration checking

Create unsigned JWT tokens for testing and development

Support for all standard JWT algorithms (HS256, RS256, ES256, etc.)

Automatic timestamp conversion to human-readable dates

Color-coded token status indicators (valid, expired, not-yet-valid)

Quick actions for setting standard time claims (iat, exp, nbf)

Copy individual sections or entire decoded JSON

Sample tokens for learning JWT structure

Privacy-focused - all processing happens in your browser

Common Use Cases

API Authentication Debugging: Decode tokens from API responses to verify claims, check expiration times, and understand why authentication might be failing in your applications.

Token Development and Testing: Create test tokens with specific claims and expiration times for development environments without needing server-side token generation.

Security Auditing: Analyze JWT tokens to ensure they don't contain sensitive information in the payload and verify proper algorithm usage for your security requirements.

Mobile App Development: Debug authentication flows in mobile applications by decoding tokens received from backend services to verify correct user data and permissions.

Microservices Architecture: Validate tokens passed between services to ensure proper claims propagation and understand authorization failures in distributed systems.

Third-party Integration: Decode tokens from OAuth providers or partner APIs to understand what data is being shared and verify integration configurations.

Frequently Asked Questions

What are the three parts of a JWT token?

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A JWT consists of three parts separated by dots: 1) Header - Contains metadata about the token including the signing algorithm and token type. 2) Payload - Contains claims (data) about the entity and additional metadata like expiration time. 3) Signature - Ensures the token hasn't been altered and verifies the sender. Each part is Base64Url encoded, making the token URL-safe.

Is it safe to decode JWT tokens?

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Yes, decoding JWT tokens is safe and is actually intended behavior. JWTs are designed to be decoded by recipients - they're encoded, not encrypted. The security comes from the signature which verifies the token hasn't been tampered with. However, you should never put sensitive information like passwords in JWT payloads since anyone can decode them.

What's the difference between JWT expiration claims?

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JWT has three time-related standard claims: 'iat' (issued at) indicates when the token was created, 'exp' (expiration time) specifies when the token expires and should no longer be accepted, and 'nbf' (not before) indicates the time before which the token should not be accepted. All use Unix timestamps (seconds since January 1, 1970 UTC).

Why does the tool create unsigned tokens?

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For security reasons, this tool creates unsigned tokens (alg: none) which are only suitable for testing and development. Creating properly signed tokens requires a secret key (for HMAC algorithms) or private key (for RSA/ECDSA algorithms) which should never be exposed in a client-side tool. For production use, generate tokens on your secure backend server.

What are JWT standard claims?

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JWT defines seven standard claims: 'iss' (issuer) identifies who created the token, 'sub' (subject) identifies the token subject (usually a user), 'aud' (audience) identifies intended recipients, 'exp' (expiration) sets when the token expires, 'nbf' (not before) sets when the token becomes valid, 'iat' (issued at) indicates creation time, and 'jti' (JWT ID) provides a unique identifier. You can also add custom claims for application-specific data.

How do I validate a JWT signature?

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JWT signature validation requires the secret key (for HMAC) or public key (for RSA/ECDSA) used to sign the token. This tool shows the signature but cannot validate it without the key. For production validation, use server-side libraries that securely store keys and implement proper validation logic including algorithm verification to prevent attacks.

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