HeaderCheck is a free Chrome extension designed to enhance web security by auditing HTTP response headers. This tool operates entirely offline, ensuring user privacy while analyzing the security posture of active web pages. It implements a deterministic weighted scoring model (SCMto provide a clear score ranging from 0 to 100, based on the presence and validity of essential security headers such as CSP, HSTS, and X-Frame-Options.

The extension features a clean, minimal interface that prioritizes user experience while providing instant analysis without any remote calls or telemetry. It distinguishes between graded and informational headers, making the results easy to understand. HeaderCheck is aligned with modern security best practices and EU regulations, focusing on transport integrity and minimizing referrer data, making it an essential tool for users concerned about online security.