Cryptographically verify JSON Web Tokens (JWT) using Web Crypto Subtle API with zero data uploads.
Execution runs 100% locally inside the browser sandbox using HTML5 Canvas, Web Cryptography Subtle API, and Web Workers. Zero egress.
Zero network latency. Operates completely offline with zero dependencies on third-party backend servers or cloud services.
Built according to official RFC specifications, cryptographic test vectors, and enterprise-grade data transformation standards.
Paste your raw JSON Web Token (JWT) string into the text area.
Enter the HMAC secret or public key corresponding to the token algorithm.
Click 'Verify Signature' to run the cryptographic validation engine.
No. All cryptographic verification and Base64Url decoding executes 100% locally in your browser memory.
Yes, it parses the standard `exp` Unix timestamp claim and compares it with your current system time.
Zero-egress companion tools in the Security & Network suite
Audit CSP, HSTS, X-Frame-Options, and security headers with OWASP grading (A+ to F).
Measure cryptographic randomness, Shannon entropy (0-8 bits/byte), Chi-square test, and byte distributions.
Generate secure RFC 6238 Base32 TOTP secret keys and standard otpauth:// URIs for Google Authenticator.
Construct and validate HTTP CSP headers and meta tags.
