JWT Parser
Parse, decode, and validate JSON Web Tokens (JWT) with header, payload, and signature analysis
JWT Parser
Parse, decode, and validate JSON Web Tokens (JWT) with header, payload, and signature analysis
JWT Token Parser
Symmetric Algorithms
Asymmetric Algorithms
Example JWT Tokens
About JWT Token Parsing
JSON Web Tokens (JWT) are compact, URL-safe tokens that represent claims between parties. They consist of three Base64-encoded parts separated by dots: header, payload, and signature. JWT parsing allows developers to examine token contents, validate structure, verify expiration, and debug authentication issues in web applications and APIs.
- Decode JWT headers to see algorithm and token type
- Extract payload claims including user data and permissions
- Analyze token expiration and issued dates
- Validate token structure and format
- Debug authentication and authorization issues
JWT Token Structure
Token Components
- Header: Algorithm and token type
- Payload: Claims and user data
- Signature: Verification hash
- Format: header.payload.signature
- Encoding: Base64URL for each part
- Separator: Dot (.) between components
Common Claims
- iss: Issuer (who created the token)
- sub: Subject (user identifier)
- aud: Audience (intended recipient)
- exp: Expiration time (Unix timestamp)
- iat: Issued at time
- nbf: Not before time
Frequently Asked Questions
How to parse json web token?
To parse a JSON Web Token, split the token string by the dot (.) separator into three parts: header, payload, and signature. Then Base64URL-decode the header and payload sections to reveal the JSON data inside. utilAZ provides a free online JWT parser that instantly decodes and displays all token components with formatted output.
What is jwt parser used for?
A JWT parser is used to decode and inspect the contents of JSON Web Tokens during development and debugging. It helps developers view the header algorithm, extract payload claims like user ID and expiration time, and validate token structure. This is essential when troubleshooting authentication flows, OAuth2 integrations, and API authorization issues.
How to decode jwt in javascript?
In JavaScript, you can decode a JWT by splitting the token on dots and using atob() or Buffer.from() to Base64-decode the header and payload parts. For example: JSON.parse(atob(token.split('.')[1])) extracts the payload. For Node.js, libraries like jsonwebtoken or jose provide full parsing and verification capabilities.
Is online jwt parser safe?
An online JWT parser is safe for development tokens because it only decodes the Base64-encoded content without needing the secret key. The utilAZ JWT parser processes tokens entirely in your browser, so no data is sent to any server. However, avoid pasting production tokens containing sensitive user data into any online tool.
How to verify jwt signature after parsing?
To verify a JWT signature, you need the signing key (shared secret for HS256 or public key for RS256/ES256). Recreate the signature by hashing the header and payload with the key using the algorithm specified in the header, then compare it to the token signature. Libraries like jsonwebtoken (Node.js) or PyJWT (Python) handle this verification automatically.
JWT Token Examples
Sample JWT Analysis:
JWT Signing Algorithms
Symmetric Algorithms:
Asymmetric Algorithms:
JWT Security Best Practices
Security Guidelines:
Common Vulnerabilities:
Standard JWT Claims
Reserved Claims:
Custom Claims Examples:
Common Use Cases
- Debugging authentication issues
- Analyzing token expiration problems
- Inspecting user claims and permissions
- Validating token structure and format
- API integration testing
- Understanding OAuth token contents
- Troubleshooting SSO implementations
- Learning JWT structure and claims