Spectra Guard API is the core backend security analysis engine powering the Spectra Guard website security assessment platform. Designed with Cloudflare Workers and modern JavaScript, it provides a lightweight, serverless solution for performing passive website security analysis without intrusive testing methods. The API evaluates publicly available website information to identify security configurations, privacy signals, and potential weaknesses. The engine analyzes HTTPS implementation, HTTP security headers, cookie security attributes, third-party tracking technologies, website technology stacks, and possible information exposure indicators. It processes scan results through a risk-based scoring system and generates structured security reports containing security scores, risk levels, detected issues, vulnerabilities, and actionable recommendations. Spectra Guard API is built with a focus on safe, ethical, and educational cybersecurity analysis. It does not perform exploitation, unauthorized penetration testing, or invasive attacks. Instead, it helps developers, students, and security enthusiasts understand modern web security practices and improve awareness of website protection mechanisms. The project demonstrates the use of serverless architecture, API development, web security concepts, automated analysis workflows, and cloud-based deployment using Cloudflare Workers.