A JSON Web Token (JWT) is a compact, URL-safe means of representing claims between two parties. It consists of three parts: header, payload, and signature, each separated by dots.

How do I read a JWT token?

Simply paste your JWT into our decoder. It will automatically split and decode the three parts: the header (algorithm info), payload (data), and signature (verification code).

JWTs are secure when used properly. They're signed to prevent tampering, but should never contain sensitive data as the payload is only Base64 encoded, not encrypted.

What's the difference between JWTs and session tokens?

Unlike session tokens that reference server-side data, JWTs contain the actual data (claims) within the token itself, making them self-contained and ideal for stateless authentication.

How does JWT signature verification work?

The signature is created using the encoded header, encoded payload, and a secret key. The server can verify the token hasn't been tampered with by recreating the signature using the same secret.

What algorithms are supported for JWT?

Common algorithms include HS256 (HMAC with SHA-256), RS256 (RSA with SHA-256), and ES256 (ECDSA with SHA-256). Our decoder supports all standard JWT signing algorithms.

JWTs themselves can't be revoked, but you can implement expiration times (exp claim) or maintain a blacklist. Best practice is to keep token lifetimes short.

Should I store sensitive data in a JWT?

No, JWT payloads are Base64 encoded, not encrypted. Anyone can decode and read the payload. Only store non-sensitive claims that are necessary for your application.

Where should I store JWTs in my application?

For web applications, JWTs are typically stored in HttpOnly cookies (preferred for security) or localStorage. The choice depends on your security requirements and threat model.

How long should JWT tokens be valid?

The recommended validity period depends on your use case. Access tokens typically last 15-60 minutes, while refresh tokens might last days or weeks. Shorter periods are more secure.

Can I use JWTs for session management?

While possible, JWTs are better suited for stateless authentication. For session management, traditional server-side sessions might be more appropriate.

What claims should I include in a JWT?

Common claims include 'sub' (subject), 'iat' (issued at), 'exp' (expiration), and 'iss' (issuer). Include only the claims necessary for your application's functionality.

Why is my JWT signature invalid?

Invalid signatures usually occur due to incorrect secret keys, wrong algorithms, or token tampering. Check that you're using the correct secret and algorithm for verification.

What does 'Token expired' mean?

This error occurs when the current time is past the token's expiration time (exp claim). You'll need to refresh the token or require the user to authenticate again.

Why can't I decode my token?

If the token can't be decoded, it might be malformed or not actually be a JWT. Valid JWTs consist of three Base64URL-encoded sections separated by dots.

How do I fix 'Invalid token format'?

This error means the token doesn't follow the JWT structure (header.payload.signature). Check that the token is complete and properly formatted with two dots separating the three parts.

JWT Decoder

Decode and verify JSON Web Tokens (JWT) with our powerful online tool. Visualize header and payload data, validate signatures, and debug JWT tokens easily.

JWT Parsing

Token Validation

Header Analysis

Payload Decoder

Signature Verification

Features

Token Parsing

Parse and decode JWT tokens to view header and payload data in a readable format.

Signature Verification

Verify JWT signatures with support for multiple algorithms including HS256, RS256, and more.

Token Analysis

Analyze token structure, expiration, and claims with detailed insights.

Interesting History

Origins

JWT was created in 2010 by Auth0's CTO and Chief Architect Jon Matonis. It emerged from the need for a compact, self-contained way to transmit authentication and authorization data between parties in web applications.

Standardization

In May 2015, JWT was standardized as RFC 7519 by the Internet Engineering Task Force (IETF). This standardization helped establish JWT as a trusted format for secure information exchange.

Modern Impact

JWT has become the de facto standard for token-based authentication in modern web applications, APIs, and microservices architectures, replacing traditional session-based authentication in many cases.

Key Features

Security Features

Support for multiple signing algorithms (HS256, RS256, etc.)
Signature verification and validation
Expiration time checking
Claim validation and verification

Decoding Capabilities

Base64 header and payload decoding
JSON structure formatting
Token structure validation
Detailed token analysis

Developer Tools

Debug mode for detailed inspection
Copy and share functionality
Error explanation and suggestions
Token generation examples

Privacy Features

Client-side processing only
No server storage of tokens
Secure token handling
Data sanitization

How It Works

1. Input JWT Token

Paste your JWT token into the decoder input field. The tool automatically validates the token format.

2. Decode and Parse

The decoder splits the token into its components (header, payload, signature) and decodes the base64 content.

3. Analyze Results

View decoded data in a formatted JSON structure, check token validity, and verify signatures if needed.

Frequently Asked Questions

Basics

Fundamental concepts of JWT

Tips for Using JWT Decoder

Always verify token signatures in production environments
Check token expiration dates and issuer claims
Be cautious with sensitive data in JWT payloads
Use appropriate algorithms based on your security requirements
Keep your signing keys secure and rotate them regularly

JWT Decoder

Features

Token Parsing

Signature Verification

Token Analysis

Interesting History

Origins

Standardization

Modern Impact

Key Features

Security Features

Decoding Capabilities

Developer Tools

Privacy Features

How It Works

1. Input JWT Token

2. Decode and Parse

3. Analyze Results

Frequently Asked Questions

Basics

What is a JWT token?

How do I read a JWT token?

Are JWTs secure?

What's the difference between JWTs and session tokens?

Tips for Using JWT Decoder

Related Topics