# SEO Diagnostics SEO Diagnostics audits a web page or an entire sitemap against a broad battery of checks, far wider than a single Core Web Vitals or rich-results test. It loads each page in a real headless browser, inspects the rendered DOM, measures performance, and grades the result. Progress streams live while the audit runs, and a full categorised report is produced at the end. Open it from the **Tools** menu, or go straight to `/tools/seo`. It is public: you do not need an account. ## Running an audit 1. Paste a URL (for a single page) or a `sitemap.xml` URL. 2. Choose **Single URL** or **Sitemap**. In sitemap mode, set how many pages to crawl (up to 50). 3. Press **Run audit**. Progress appears immediately: each page is loaded, then every check runs. 4. When the audit finishes, the score, grade, per-category breakdown and every individual check with its recommendation are shown. A link opens the full standalone report. You can run one audit at a time. Targets that resolve to private or local addresses are refused. ## What gets checked The auditor groups its findings into categories: - **Crawlability and indexing** - HTTP status, redirect chains, HTTPS and HSTS, canonical tags, meta-robots and `X-Robots-Tag`, `robots.txt`, XML sitemap, URL hygiene, and mixed content. - **On-page meta and content** - title and meta description (presence and length), single H1 and heading hierarchy, content depth, language, character encoding, viewport, and favicon. - **Links** - internal and external link profile, descriptive anchor text. - **Structured data** - JSON-LD validity, recognised schema types and their required properties, microdata and RDFa detection. - **Social cards** - Open Graph and Twitter Card tags for rich link previews. - **Performance and Core Web Vitals** - Largest Contentful Paint, Cumulative Layout Shift, First Contentful Paint, Time To First Byte, page weight, request count, DOM size, compression, caching, image optimisation, and console errors. - **Mobile and accessibility** - responsive layout (no horizontal overflow), tap-target sizing, image alt coverage, and form labels. - **Security** - the common security response headers and TLS. - **AI and LLM-search readiness** - whether your primary content is in the initial HTML (server rendered) rather than JavaScript-only, presence of an `llms.txt`, and semantic HTML landmarks. Each check reports a status (pass, warn, fail or info), its severity, the observed value, and a recommendation when something can be improved. The overall score is a severity-weighted pass rate, shown as a 0-100 number and an A to F grade, with a subscore per category. ## Scoring Failing a critical check (for example a non-200 status or HTTPS) costs far more than a low-severity warning. Informational checks never affect the score. A score of 90 or above is an A. ## Ask Devii You can also run an audit in plain language through the Devii assistant: > Run SEO diagnostics on https://example.com and tell me the score. Devii queues the audit, polls it, and reports the score, grade and a link to the full report. ## Programmatic access The same audit is available over the API: `POST /tools/seo/run` to queue, `GET /tools/seo/{uid}` to poll, and `GET /tools/seo/{uid}/report` for the full report (HTML or JSON). See the [Tools (SEO Diagnostics)](/docs/tools.html) API group for request and response shapes.