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JWT Decoder/Encoder Tool

Decode, encode, and validate JSON Web Tokens (JWT) instantly. Professional-grade JWT tool with support for multiple algorithms. Perfect for developers working with authentication and API tokens.

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🔓 JWT Token Input

📋 Decoded JWT Parts

⚠️ Enter a JWT token to decode

🔴 Header

Header part will appear here...

🟣 Payload

Payload part will appear here...

🔵 Signature

Signature part will appear here...

🔧 Signing Algorithm

🔑

HS256

HMAC with SHA-256

🔐

HS512

HMAC with SHA-512

🗝️

RS256

RSA with SHA-256

⚪

None

No signature

📝 JWT Components

Header (JSON)

Payload (JSON)

Secret Key

🔒 Generated JWT

JWT Structure Breakdown

Header

Payload

Signature

✅ JWT Validation

Secret Key (for HMAC validation)

📊 Validation Results

⚠️ Enter a JWT token to validate

Complete Guide to JWT (JSON Web Tokens)

Everything you need to know about JSON Web Tokens, their structure, algorithms, and best practices for secure authentication.

🔍 What are JSON Web Tokens?

JSON Web Tokens (JWT) are a compact, URL-safe way to represent claims between two parties. They consist of three parts separated by dots: header, payload, and signature.

Stateless authentication mechanism
Self-contained information
Digitally signed for integrity
URL-safe for web transmission

🏗️ JWT Structure

A JWT consists of three Base64-encoded parts separated by dots (.):

// JWT Structure
Header.Payload.Signature

// Example JWT
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.
eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.
SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

🔐 Signing Algorithms

JWTs support various algorithms for signing and verification:

HS256: HMAC with SHA-256 (symmetric)
HS512: HMAC with SHA-512 (symmetric)
RS256: RSA with SHA-256 (asymmetric)
ES256: ECDSA with SHA-256 (asymmetric)

🎯 Common Use Cases

JWTs are widely used in modern web applications and APIs:

User authentication and authorization
API access tokens
Single Sign-On (SSO) systems
Information exchange between services
Session management in stateless apps
OAuth 2.0 and OpenID Connect

🛡️ Security Best Practices

Follow these guidelines for secure JWT implementation:

// ✅ Best Practices
- Use strong secret keys (256+ bits)
- Set appropriate expiration times
- Validate tokens on every request
- Use HTTPS for transmission
- Store tokens securely (HttpOnly cookies)
- Implement proper error handling

⚠️ Common Pitfalls

Avoid these common JWT security mistakes:

Using weak or predictable secrets
Not validating token expiration
Storing sensitive data in payload
Using "none" algorithm in production
Not implementing proper key rotation
Trusting client-side token validation

Frequently Asked Questions

What is a JWT token and how does it work? +

A JSON Web Token (JWT) is a compact, URL-safe token that represents claims between two parties. It consists of three parts: header (algorithm and token type), payload (claims), and signature (verification). The token is signed to ensure integrity and can be verified without storing session state on the server.

What's the difference between JWT signing algorithms? +

HS256 uses HMAC with SHA-256 (symmetric key), HS512 uses HMAC with SHA-512 (symmetric key), while RS256 uses RSA with SHA-256 (asymmetric keys). Symmetric algorithms use the same key for signing and verification, while asymmetric algorithms use a private key for signing and public key for verification. Choose based on your security requirements and key distribution needs.

How secure are JWT tokens? +

JWT security depends on proper implementation. They're secure when using strong secret keys, proper algorithms, HTTPS transmission, and appropriate expiration times. However, they're not encrypted by default (only signed), so don't store sensitive information in the payload. Always validate tokens server-side and use secure storage mechanisms.

Can JWT tokens be decoded without the secret key? +

Yes, the header and payload of a JWT can be decoded without the secret key since they're just Base64-encoded JSON. However, you cannot verify the signature or modify the token without the secret key. This is why you should never store sensitive information in the JWT payload - it's visible to anyone who has the token.

What are JWT claims and why are they important? +

JWT claims are pieces of information about an entity (typically the user). There are registered claims (iss, exp, iat, etc.), public claims, and private claims. Important claims include 'exp' (expiration), 'iat' (issued at), 'sub' (subject), and 'iss' (issuer). These claims help validate the token's authenticity, timing, and scope.

How do I validate a JWT token? +

JWT validation involves several steps: verify the signature using the secret key or public key, check the token hasn't expired (exp claim), verify the issuer (iss claim), ensure the token is not used before its time (nbf claim), and validate any custom claims. Always perform validation server-side for security.

What's the difference between JWT and session cookies? +

JWT tokens are stateless and self-contained, while session cookies require server-side session storage. JWTs can be used across multiple domains and services, are better for APIs and microservices, but are larger in size. Session cookies are smaller, easier to revoke, but require server storage and are limited to same-domain usage.

Is this JWT tool free to use? +

Yes, our JWT decoder/encoder tool is completely free to use with no registration required. You can decode unlimited tokens, create new JWTs, validate signatures, copy results, and download data without any charges. All processing happens in your browser for maximum security and privacy.

Can I use this tool for production JWT tokens? +

While our tool is excellent for development and testing, be cautious with production tokens containing sensitive data. The tool runs locally in your browser, but for maximum security with production tokens, use server-side validation in your applications. Our tool is perfect for learning, debugging, and understanding JWT structure.

Does this JWT tool work offline? +

Yes! Once the page loads, all JWT processing happens in your browser using JavaScript. You can decode, encode, and validate JWT tokens without an internet connection. This ensures your tokens never leave your device, providing maximum privacy and security for sensitive tokens.

JWT Decoder/Encoder Tool

🔓 JWT Token Input

📋 Decoded JWT Parts

🔧 Signing Algorithm

📝 JWT Components

🔒 Generated JWT

✅ JWT Validation

📊 Validation Results

Complete Guide to JWT (JSON Web Tokens)

🔍 What are JSON Web Tokens?

🏗️ JWT Structure

🔐 Signing Algorithms

🎯 Common Use Cases

🛡️ Security Best Practices

⚠️ Common Pitfalls

Frequently Asked Questions

200+ Forever Free Tools

Fast & Browser-Based

Mobile Optimized

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JWT Decoder/Encoder Tool

🔓 JWT Token Input

📋 Decoded JWT Parts

🔧 Signing Algorithm

📝 JWT Components

🔒 Generated JWT

✅ JWT Validation

📊 Validation Results

Complete Guide to JWT (JSON Web Tokens)

🔍 What are JSON Web Tokens?

🏗️ JWT Structure

🔐 Signing Algorithms

🎯 Common Use Cases

🛡️ Security Best Practices

⚠️ Common Pitfalls

Frequently Asked Questions

Related Developer Tools

200+ Forever Free Tools

Fast & Browser-Based

Mobile Optimized

Privacy Committed

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