Technical SEO Audit

Categories

1. Crawlability

• robots.txt: exists, valid, not blocking important resources
• XML sitemap: run "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run sitemap_discovery.py <url> --json; require a valid entry in found, and report stale or unsafe robots.txt declarations separately from working fallback locations
• Noindex tags: intentional vs accidental
• Crawl depth: important pages within 3 clicks of homepage
• JavaScript rendering: check if critical content requires JS execution
• Crawl budget: for large sites (>10k pages), efficiency matters
• Googlebot fetch limits: Googlebot fetches the first 2MB of HTML and first 64MB of a PDF (uncompressed; 15MB is the broader crawler-infra default). Long-standing, not a 2026 change, but inline base64 images, oversized inline CSS/JS, or bloated nav can push critical content/JSON-LD past the cap and out of the index. Keep key content + structured data within the first 2MB.
• Crawl rate auto-adjusts (backs off on 5xx/slow responses); there is no manual crawl-rate control (the legacy Search Console setting was removed Jan 2024). Influence crawling via sitemaps, server responsiveness, and robots controls.
• Google's canonical crawling/robots reference moved to developers.google.com/crawling (migrated 2025-11-20); IP-range files relocated to /crawling/ipranges/ and googlebot.json was renamed common-crawlers.json.
• AMP has no separate ranking advantage. Since 2026-07-01, Google Search sends users directly to publisher-hosted AMP URLs, so do not recommend AMP Cache, AMP Viewer, or signed exchange maintenance. Audit AMP against the same content, action-parity, and quality requirements as other pages.

AI Crawler Management

As of 2025-2026, AI companies actively crawl the web to train models and power AI search. Managing these crawlers via robots.txt is a critical technical SEO consideration.

Known AI crawlers:

Key distinctions: - Blocking Google-Extended prevents Gemini training use but does NOT affect Google Search indexing or AI Overviews (those use Googlebot) - Blocking GPTBot prevents OpenAI training but does NOT affect ChatGPT Search citability, which is governed by OAI-SearchBot, nor user-triggered browsing (ChatGPT-User). Check OAI-SearchBot for any citability claim; GPTBot status is evidence about training use only - Blocking ClaudeBot prevents Anthropic model training but does NOT affect citability in Claude's own search features, which is governed by Claude-SearchBot (per Anthropic's crawler support article). Check Claude-SearchBot for any Claude-search citability claim; ClaudeBot status is evidence about training use only - Blocking Applebot-Extended opts out of Apple Intelligence / generative-model training use but does NOT affect discoverability via Siri, Spotlight, or Safari, which follows Applebot (per Apple's support article); Applebot-Extended does not itself crawl - ~3-5% of websites now use AI-specific robots.txt rules

Example, selective AI crawler blocking:

# Allow search indexing, block AI training crawlers
User-agent: GPTBot
Disallow: /

User-agent: Google-Extended
Disallow: /

User-agent: Bytespider
Disallow: /

# Allow all other crawlers (including Googlebot for search)
User-agent: *
Allow: /

Recommendation: Consider your AI visibility strategy before blocking. Being cited by AI systems drives brand awareness and referral traffic. Cross-reference the seo-geo skill for the full AI crawler/fetcher taxonomy.

User-triggered fetchers ignore robots.txt by design. Google now documents Google-Agent (Project Mariner, agentic browsing) plus Google-NotebookLM and Google Messages as user-triggered fetchers that cannot be blocked via robots.txt. Use server-side access controls instead. By contrast, Google-Extended and Google-CloudVertexBot obey robots.txt. Emerging: Web Bot Auth (RFC 9421) lets bots authenticate cryptographically via a Signature-Agent header + key directory at agent.bot.goog (used by Google-Agent); reverse-DNS verification remains the fallback.

2. Indexability

• Canonical tags: self-referencing, no conflicts with noindex
• Duplicate content: near-duplicates, parameter URLs, www vs non-www
• Canonicalization fixes can take time: Google may retain corrected pages in a duplicate cluster for up to two weeks while re-evaluating them. Do not interpret an unchanged canonical immediately after a fix as proof that the fix failed.
• Thin content: pages below minimum word counts per type
• Pagination: rel=next/prev or load-more pattern
• Hreflang: correct for multi-language/multi-region sites
• Index bloat: unnecessary pages consuming crawl budget

3. Security

• HTTPS: enforced, valid SSL certificate, no mixed content
• Security headers:
• Content-Security-Policy (CSP)
• Strict-Transport-Security (HSTS)
• X-Frame-Options
• X-Content-Type-Options
• Referrer-Policy
• HSTS preload: check preload list inclusion for high-security sites
• Back-button hijacking (spam-policy violation, malicious practices): flag pages that defeat the Back button via history.pushState/replaceState (including scripts injected by third-party ad/library platforms). Added to Google's spam policies 2026-04-13; enforcement live since 2026-06-15 (manual actions + automated demotions): treat as Critical.

4. URL Structure

• Clean URLs: descriptive, hyphenated, no query parameters for content
• Hierarchy: logical folder structure reflecting site architecture
• Redirects: no chains (max 1 hop), 301 for permanent moves
• URL length: flag >100 characters
• Trailing slashes: consistent usage

5. Mobile Optimization & Page Experience

• Responsive design: viewport meta tag, responsive CSS
• Touch targets: minimum 48x48px with 8px spacing
• Font size: minimum 16px base
• No horizontal scroll
• Mobile-first indexing: Googlebot Smartphone is the primary crawler (rollout completed 2024). A mobile version is not strictly required (Google says "very strongly recommended"), sites that don't work on mobile can still be indexed, but the real risk is content/parity loss, not hard exclusion.
• Mobile/desktop content parity (highest-value mobile check): equivalent primary content, matching robots meta tags, matching titles/descriptions, equivalent structured data, crawlable resources; avoid lazy-loading primary content that requires user interaction.
• Intrusive interstitials / ad density: flag full-page interstitials, standalone consent-redirect pages, persistent blocking dialogs, and excessive/distracting ad density (a named page-experience aspect). Acceptable: small banners, standard CMS/legal dialogs.
• "Read more" deep links: keep key content immediately visible on load (not behind tabs/accordions), don't hijack scroll on load, and preserve URL hash fragments, content hidden behind expandable sections is less likely to qualify.

Page experience is guidance, not a single ranking system. Only Core Web Vitals feeds ranking directly; HTTPS is a confirmed but lightweight signal (affects <~1% of queries). Relevance can still win even when page experience is sub-par, so don't over-weight security headers. Note: the standalone Page Experience report was removed from Search Console (monitor via the Core Web Vitals + HTTPS reports).

6. Core Web Vitals

• LCP (Largest Contentful Paint): target <=2.5s
• INP (Interaction to Next Paint): target <=200ms
• INP replaced FID on March 12, 2024. FID was removed from Chrome's field-data tools (CrUX API, PageSpeed Insights) on September 9, 2024 (Lighthouse is a lab tool that never reported FID). Do NOT reference FID anywhere.
• CLS (Cumulative Layout Shift): target <=0.1
• Evaluation uses 75th percentile of real user data
• Use PageSpeed Insights API or CrUX data if MCP available

7. Structured Data

• Detection: JSON-LD (preferred), Microdata, RDFa
• Validation against Google's supported types
• See seo-schema skill for full analysis

8. JavaScript Rendering

• Check if content visible in initial HTML vs requires JS
• Identify client-side rendered (CSR) vs server-side rendered (SSR)
• Flag SPA frameworks (React, Vue, Angular) that may cause indexing issues
• If dynamic rendering is detected, flag it as technical debt rather than a valid setup. Google documents it as "a workaround and not a recommended solution" because of the added complexity and resource cost. See https://developers.google.com/search/docs/crawling-indexing/javascript/dynamic-rendering

Recommended rendering strategy:

Preferred frameworks: Next.js, Astro, React Router v7 (Remix), SvelteKit

JavaScript SEO: Canonical & Indexing Guidance (December 2025)

Google updated its JavaScript SEO documentation in December 2025 with critical clarifications:

1. Canonical conflicts: If a canonical tag in raw HTML differs from one injected by JavaScript, Google may use EITHER one. Ensure canonical tags are identical between server-rendered HTML and JS-rendered output.
2. noindex with JavaScript: If raw HTML contains <meta name="robots" content="noindex"> but JavaScript removes it, Google MAY still honor the noindex from raw HTML. Serve correct robots directives in the initial HTML response.
3. Non-200 status codes: Google does NOT render JavaScript on pages returning non-200 HTTP status codes. Any content or meta tags injected via JS on error pages will be invisible to Googlebot.
4. Structured data in JavaScript: Product, Article, and other structured data injected via JS may face delayed processing. For time-sensitive structured data (especially e-commerce Product markup), include it in the initial server-rendered HTML.

Best practice: Serve critical SEO elements (canonical, meta robots, structured data, title, meta description) in the initial server-rendered HTML rather than relying on JavaScript injection.

9. IndexNow Protocol

• Check if site supports IndexNow for Bing, Yandex, Naver
• Supported by search engines other than Google
• Recommend implementation for faster indexing on non-Google engines

Agent-Friendly Pages & Agentic Browsing

AI agents (not just AI summarizers) increasingly read sites through three channels: vision models on screenshots, raw HTML/DOM, and the accessibility tree (the cleanest signal). Audit criteria: semantic HTML (real <button> and <a>, not <div onclick>), label associations, interactive target sizing, layout stability across templates, cursor: pointer correctness, live in references/agent-friendly-pages.md.

Google now ships a Lighthouse Agentic Browsing category (default-on since Lighthouse 13.3.0, Chrome 150+; buckets: agent-centric accessibility, CLS + llms.txt, three WebMCP audits). It reports a fractional pass-ratio (X of N), not a 0-100 score, keep that distinct from this skill's own Agent-UX 0-100 heuristic below. Lighthouse 13.4.1 re-enabled the category through the PSI API. It is also available through Lighthouse CLI with --only-categories=agentic-browsing, DevTools, and the PSI web UI. See references/agent-friendly-pages.md.

Audit command

# Render with Playwright + capture accessibility tree, then score
"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run agent_ux_check.py https://example.com --json

The scanner outputs an Agent-UX score (0-100) plus itemized issues: - HTML findings: real buttons / anchors, <div onclick> widgets, semantic landmarks, inputs without <label for>, inputs without ARIA labels - Accessibility tree findings: total nodes, interactive nodes, unnamed interactive elements, role="generic" ratio

The accessibility-tree snapshot uses Chromium's Accessibility.getFullAXTree CDP command through Playwright. To capture the tree without scoring, use "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run render_page.py <url> --a11y-tree --json.

Surface findings as opportunities, not failures; don't gate audits on a sub-100 Agent-UX score. WebMCP origin-trial/sign-up status needs verification, and absence of WebMCP support is still an opportunity, not a defect.

Output

Technical Score: XX/100

Category Breakdown

Critical Issues (fix immediately)

High Priority (fix within 1 week)

Medium Priority (fix within 1 month)

Low Priority (backlog)

DataForSEO Integration (Optional)

If DataForSEO MCP tools are available, use on_page_instant_pages for real page analysis (status codes, page timing, broken links, on-page checks), on_page_lighthouse for Lighthouse audits (performance, accessibility, SEO scores), and domain_analytics_technologies_domain_technologies for technology stack detection.

Google API Integration (Optional)

If Google API credentials are configured, use "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run pagespeed_check.py <url> --json for real PSI + CrUX field data (replaces lab-only CWV estimates), "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run crux_history.py <url> --json for 25-week CWV trends, and "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run gsc_inspect.py <url> --json for real indexation status per URL.

Auditing a Local or Private Host

url_safety refuses loopback and private addresses by default, so http://localhost:3000 and a staging host on Tailscale fail with "Blocked hostname" or "Blocked IP literal". That default is deliberate: these scripts follow URLs found on the pages they crawl.

To audit a pre-deployment host, the operator names it in CLAUDE_SEO_LOCAL_TARGETS, a comma-separated list of host or host:port entries:

CLAUDE_SEO_LOCAL_TARGETS="localhost:3000,127.0.0.1:8080,100.101.102.103" \
  "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run fetch_page.py http://localhost:3000/

What it does and does not cover:

host:port matches that port only; a bare host matches any port. With the variable unset the policy is unchanged. Never suggest setting it for a host the user does not control. See SECURITY.md.

Error Handling