SEO Scanner is the most complete free technical SEO audit tool. Paste any URL → get a full-site crawl via sitemap or deep crawling. What it checks: → Meta tags, headings, images, canonical, robots, structured data → Google PageSpeed Insights scores (performance, accessibility, SEO) → Security headers (HTTPS, HSTS, CSP, X-Frame-Options) → Duplicate content detection across the entire site → Internal link architecture analysis