Schema markup is JSON-LD structured data you add to your pages so search engines can understand your content type. Google uses it to display rich results — star ratings, FAQ dropdowns, recipe cards, event listings — directly in search results, which significantly improves click-through rates.

At minimum: title (50–60 chars), meta description (150–160 chars), canonical URL, og:title, og:description, og:image (1200×630px), twitter:card. These cover both search engine indexing and social media sharing appearance.

Robots.txt tells crawlers which pages to skip. Typically you block /admin/, /private/, and duplicate parameter URLs. Always include a Sitemap: directive pointing to your sitemap.xml. Avoid blocking CSS and JS files — Google needs them to render your pages.

There is no exact magic number. A density of 1–3% for your primary keyword is common guidance. More important is natural usage — write for readers first. High density (above 4–5%) risks being seen as keyword stuffing, which can hurt rankings.

Security headers like Content-Security-Policy, HSTS, and X-Frame-Options protect your site from XSS, clickjacking, and protocol downgrade attacks. They also signal to search engines that your site is well-maintained, which can indirectly support rankings.

Most run entirely in your browser — meta tag generator, schema generator, robots.txt generator, sitemap generator, OG preview, and keyword density checker all work offline. Only the HTTP Headers Checker makes an outbound request to check a URL's headers.