JWTLens isn't just another JWT decoder. It's a comprehensive security analysis platform that helps developers, security researchers, and penetration testers identify critical vulnerabilities in JWT implementations.
Unlike basic decoders, JWTLens performs 20+ security checks including algorithm confusion, injection attacks, and privilege escalation vulnerabilities.
Instantly identify XSS, SQL injection, weak signatures, and other critical security flaws in your JWT tokens with detailed severity ratings.
All analysis happens in your browser. Your JWT tokens never leave your device, ensuring complete privacy and security of sensitive data.
Get detailed security reports with severity levels, vulnerability descriptions, and actionable remediation steps for your development team.
Powered by advanced client-side algorithms, JWTLens provides instant analysis without server delays or API limits.
No registration, no limits, no hidden costs. Access enterprise-grade JWT security analysis tools completely free forever.
JSON Web Tokens (JWTs) are a compact, URL-safe way to represent claims between two parties. Think of them as digital ID cards that contain information about a user and are used to authenticate and authorize access to web applications.
A JWT consists of three Base64-encoded parts separated by dots (.)
The header specifies how the token should be verified. It contains the algorithm (like HS256, RS256) and the token type.
The payload contains claims - statements about the user and additional metadata. There are three types of claims:
The signature ensures the token hasn't been tampered with. It's created by encoding the header and payload, then signing with a secret key.
Understanding these vulnerabilities is crucial for building secure applications:
Attackers change the algorithm from RS256 to HS256, using the public key as the HMAC secret to forge tokens.
Setting algorithm to "none" removes signature verification entirely, allowing anyone to create valid tokens.
Using predictable or short secret keys makes tokens vulnerable to brute force attacks.
Tokens without expiration (exp claim) remain valid forever, increasing security risk if compromised.
Storing sensitive information in JWT payload exposes it since JWTs are only base64 encoded, not encrypted.
Malicious scripts in JWT claims can lead to Cross-Site Scripting attacks when displayed in applications.
Regular security testing is essential for maintaining secure JWT implementations:
Gather JWT tokens from your application
Validate token format and encoding
Test for vulnerabilities and weaknesses
Fix identified issues and retest
Absolutely! JWTLens processes everything locally in your browser. Your JWT tokens never leave your device or get sent to any server. All analysis happens client-side using JavaScript, ensuring complete privacy and security of your sensitive data.
While most tools only decode JWTs, JWTLens provides comprehensive security analysis. It checks for 20+ vulnerabilities including algorithm confusion, XSS attacks, weak signatures, and injection vulnerabilities. It's like having a security expert review every token.
Yes! JWTLens is designed for security professionals. It identifies vulnerabilities like algorithm confusion attacks, signature bypass attempts, and privilege escalation issues. Perfect for security assessments and penetration testing scenarios.
JWTLens uses industry-standard security checks based on OWASP guidelines and real-world attack patterns. Each finding includes severity levels and detailed explanations to help you understand and fix issues properly.
No installation required! JWTLens runs entirely in your web browser. Simply visit the website, paste your JWT token, and get instant security analysis. It works on any device with a modern web browser.
Definitely! Each vulnerability finding includes detailed explanations, examples, and remediation steps. JWTLens serves as both a practical tool and an educational resource for understanding JWT security best practices.