JSON Web Token (JWT) is an open standard that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. The information can be verified and trusted because it is digitally signed.

What are the parts of a JWT?

A JWT consists of three parts separated by dots: Header (algorithm & token type), Payload (claims/data), and Signature. Each part is base64url encoded, resulting in a structure like 'xxxxx.yyyyy.zzzzz'.

Claims are statements about an entity (typically, the user) and additional data. There are three types of claims: registered (predefined), public (custom defined), and private (agreed upon between parties).

How do I use this JWT encoder?

Simply input your payload data, select a signing algorithm, provide the secret key or keypair, and click generate. The tool will create a signed JWT token that you can use in your applications.

Which algorithm should I choose?

For symmetric signing, HS256 is commonly used. For asymmetric signing, RS256 is recommended. Choose based on your security requirements - RS256 is preferred for public-facing applications as it uses public/private key pairs.

JWTs are secure when implemented correctly. Key security practices include using strong secrets/keys, implementing proper key management, setting appropriate expiration times, and validating tokens properly.

Can JWT be encrypted?

Yes, while standard JWTs are signed but not encrypted, you can use JWE (JSON Web Encryption) to encrypt the token. However, encryption is typically not necessary if you're not storing sensitive information in the token.

What about token storage?

Store JWTs securely - typically in HttpOnly cookies for web applications. Avoid storing in localStorage due to XSS vulnerabilities. Always implement proper token refresh mechanisms and revocation strategies.

How do I validate a JWT?

To validate a JWT: 1) Verify the signature using the secret/public key, 2) Check the expiration time (exp claim), 3) Verify the issuer (iss claim) if applicable, 4) Check any custom claims required by your application.

What's the maximum size of a JWT?

While there's no strict size limit, it's recommended to keep JWTs small (under 8KB) as they're often sent in HTTP headers. Large tokens can impact performance and may exceed server limits.

How do I handle token expiration?

Set reasonable expiration times using the 'exp' claim. Implement refresh token mechanisms for longer sessions. Always validate expiration times when verifying tokens, and handle expired token errors gracefully.

JWTs are stateless and cannot be directly revoked. Implement a blacklist/database of invalidated tokens, keep token expiration times short, or use refresh token rotation patterns for revocation-like functionality.

Why is my token invalid?

Common causes include: expired tokens, incorrect signing keys, modified token content, wrong algorithm selection, or malformed JSON in the payload. Check the token on jwt.io for detailed debugging.

What causes 'Invalid Signature'?

This usually means either the wrong key is being used for verification, the token has been tampered with, or there's a mismatch in the signing algorithm between encoding and decoding.

Why am I getting Base64 errors?

Base64 errors typically occur when the token is malformed or contains invalid characters. Ensure you're using the complete token and that it hasn't been truncated or modified during transmission.

How do I fix 'Token Expired'?

This is not an error but expected behavior when a token's exp claim has passed. Implement proper token refresh mechanisms, ensure your system clocks are synchronized, and handle expiration gracefully in your application.

JWT Encoder/Decoder

Create, decode, and verify JSON Web Tokens (JWT) with our comprehensive JWT tool. Supports multiple signing algorithms, custom claims, and token validation.

JWT Encoding

JWT Decoding

Multiple Algorithms

Token Validation

Custom Claims

Algorithm

Secret/Key

Payload (JSON)

Features

Multiple Algorithms

Support for HS256, HS384, HS512, RS256, RS384, RS512, and more signing algorithms.

Custom Claims

Add and edit custom claims in the payload with JSON validation and formatting.

Token Verification

Verify JWT signatures and validate token claims including expiration and issuer.

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 widely-adopted industry standard for token-based authentication.

Modern Impact

JWT has become fundamental to modern web architecture, especially in microservices and Single Page Applications (SPAs). It's now supported by major platforms and frameworks, making it the de facto standard for stateless authentication.

Key Features

Security Features

Multiple signing algorithms (HS256, RS256, etc.)
Signature verification and validation
Expiration time handling
Claim-based security

Token Management

Custom claims support
Token debugging and inspection
Base64 encoding/decoding
JSON payload formatting

Development Tools

Real-time token preview
Error validation and feedback
Copy to clipboard functionality
Token structure visualization

Advanced Options

Public/private key pair support
Custom header modifications
Token verification options
Multiple output formats

How It Works

Encoding JWT

1. Enter your payload data (claims)
2. Select a signing algorithm
3. Provide the secret key or keypair
4. Generate the JWT token

Decoding JWT

1. Paste your JWT token
2. View the decoded header and payload
3. Verify the signature with your key
4. Check token validity and claims

Frequently Asked Questions

Basics

Fundamental concepts of JWT

Security Notice

This tool is for development and testing purposes only. Never share sensitive keys or tokens. For production use, implement proper security measures and use secure key management practices.

JWT Encoder/Decoder

Features

Multiple Algorithms

Custom Claims

Token Verification

Interesting History

Origins

Standardization

Modern Impact

Key Features

Security Features

Token Management

Development Tools

Advanced Options

How It Works

Encoding JWT

Decoding JWT

Frequently Asked Questions

Basics

What is a JWT?

What are the parts of a JWT?

What are JWT claims?

How do I use this JWT encoder?

Security Notice

Related Topics