Scanline: Site Health, Security & Stack Auditor

Audit any site locally: tech stack, security headers, Core Web Vitals, SEO, accessibility & privacy. Nothing leaves your browser.

Scanline is a browser extension that tells you what a website is built with, how secure it is, and where it might be falling short. One click on any page and you get a full breakdown of the technologies running behind the scenes, the security headers being sent (or missing), performance red flags, and SEO basics. WHAT IT DOES Tech Stack Detection Scanline looks at the DOM, script sources, meta tags, class names, and a bunch of other signals to figure out what's powering a site. It identifies the JavaScript framework or library in use, the CMS or e-commerce platform, any CSS frameworks, analytics tools, and the CDN serving the site. New detections are added regularly, and the results are broken out by category in the Stack tab so you can see exactly what was found and how confident the detection is. Security Analysis The extension checks whether a site is served over HTTPS, flags mixed content issues, and inspects the security headers being returned by the server. This includes Content-Security-Policy, Strict-Transport-Security, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, and Permissions-Policy. It also looks at how many scripts are loaded from external origins, whether there are inline scripts, and if forms are missing action attributes. Performance Metrics Scanline pulls real timing data from the browser's Performance API: DOM Content Loaded, page load time, time to first byte, and DOM interactive. It also counts DOM elements, external scripts, and stylesheets to flag pages that might be overloaded. Images without alt text are tracked too. SEO and Health Checks Basic but important SEO signals are covered: page title, meta description, viewport tag, favicon, H1 tag count, Open Graph tags, canonical URL, robots meta, and HTML lang attribute. Each check tells you whether the element is present and correct or missing entirely. Scoring Every scan produces a score out of 100 based on how many checks pass, warn, or fail. The score is broken down by category (Security, Performance, SEO) so you can see at a glance where a site is strong and where it needs work. HOW TO USE IT Install the extension, navigate to any website, and click the Scanline icon in your toolbar. The popup will analyze the current page and show results across five tabs: Overview, Stack, Security, Performance, and SEO. The Overview tab gives you a quick summary with pass/warn/fail counts and category scores. The other tabs show detailed check results. WHY YOU MIGHT WANT THIS If you are a developer doing competitor research, a designer checking a potential client's site, a security-conscious user curious about what a site is sending to your browser, or just someone who likes knowing what is under the hood of every website you visit, Scanline gives you that information without leaving the page. It runs entirely in your browser. No data is sent to any external server. Everything is processed locally. PRIVACY Scanline does not collect, store, or transmit any user data. All analysis happens locally in the browser. The extension does not phone home, does not use analytics, and does not track you in any way. PERMISSIONS Scanline requests access to the active tab and uses webRequest to read response headers for security analysis. These permissions are used solely for the scanning functionality and nothing else. The extension does not read or modify page content beyond what is needed for analysis.