🔐 JWT Decoder
Comprehensive JWT token decoder offering parsing, validation, security analysis, and educational insights for professional JWT token development and security assessment workflows.
JWT Token Analysis Results:
🔐 JWT Token Analysis
HS256
JWT
Valid Format
📋 Header
{
"alg": "HS256",
"typ": "JWT"
}📦 Payload
{
"sub": "1234567890",
"name": "John Doe",
"iat": 1516239022,
"exp": 1735689600,
"aud": "example-api",
"iss": "example-auth"
}🔒 Security Analysis
- Algorithm: HS256 (HMAC with SHA-256) - Symmetric key algorithm
- Token appears valid and well-formed
- Contains standard claims: subject, issuer, audience, expiration
- Expiration time is set (good security practice)
⚠️ Security Reminder: This is client-side educational analysis only. Never rely on client-side JWT validation for security decisions. Always validate JWTs server-side with proper secret verification!
How to Use This JWT Decoder
How to Use the JWT Decoder:
- Paste your JWT token into the input field (complete token with header.payload.signature)
- Choose validation options like signature verification and expiration checking
- Enable security analysis to identify potential vulnerabilities
- Click "Decode JWT" to parse and analyze your token
- Review header, payload, and security analysis results
- Check expiration status and token validity information
Security Note: This is a client-side educational tool. Never rely on client-side JWT validation for security decisions. Always validate JWTs server-side in production!
How It Works
Educational JWT Processing Technology:
Our decoder uses client-side JavaScript for educational JWT token analysis:
- Structure Parsing: Splits JWT into header, payload, and signature components
- Base64 Decoding: Decodes header and payload from Base64URL encoding
- JSON Parsing: Converts decoded components to readable JSON format
- Security Analysis: Identifies algorithms, vulnerabilities, and security patterns
Educational Features:
- Real-time JWT structure validation and format checking
- Algorithm identification and security risk assessment
- Expiration and timing analysis with clear warnings
- Educational security insights and best practices guidance
When You Might Need This
- • API authentication token debugging and analysis
- • JWT token structure validation for development workflows
- • Authentication system integration testing and verification
- • Security auditing of JWT implementations and token structure
- • Vulnerability assessment of JWT algorithms and configuration
Frequently Asked Questions
Is it safe to decode JWT tokens using this client-side tool?
This tool is designed for educational and development purposes. It processes tokens entirely in your browser without transmitting data to servers. However, never rely on client-side JWT validation for production security decisions - always validate JWTs server-side with proper secret verification.
What security issues can this tool help identify in JWT tokens?
The tool analyzes algorithm security (detecting insecure 'none' algorithm), validates expiration times, checks for missing security claims (iss, aud, exp), and provides recommendations for secure JWT implementation practices.
Can this tool verify JWT signatures?
No, signature verification requires the secret key or public key, which should never be shared or entered into client-side tools. This tool focuses on structure analysis, claims validation, and security education rather than cryptographic verification.
How can I use this tool for API development?
Use it to decode and analyze JWT tokens from your APIs, validate token structure and claims, debug authentication issues, and ensure your tokens follow security best practices before deployment.
What JWT algorithms does this tool support?
The tool supports analysis of all standard JWT algorithms including HS256/384/512 (HMAC), RS256/384/512 (RSA), ES256/384/512 (ECDSA), and can identify the insecure 'none' algorithm with appropriate security warnings.