1. Crawlability

robots.txt: exists, valid, not blocking important resources
XML sitemap: run 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:

Crawler	Company	robots.txt token	Purpose
GPTBot	OpenAI	`GPTBot`	Model training
ChatGPT-User	OpenAI	`ChatGPT-User`	Real-time browsing
ClaudeBot	Anthropic	`ClaudeBot`	Model training
PerplexityBot	Perplexity	`PerplexityBot`	Search index + training
Bytespider	ByteDance	`Bytespider`	Model training
Google-Extended	Google	`Google-Extended`	Gemini training (NOT search)
CCBot	Common Crawl	`CCBot`	Open dataset

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 prevent ChatGPT from citing your content via browsing (ChatGPT-User)
~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
Verify dynamic rendering setup if applicable

JavaScript SEO: Canonical & Indexing Guidance (December 2025)

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

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.
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.
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.
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-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-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

Category	Status	Score
Crawlability	pass/warn/fail	XX/100
Indexability	pass/warn/fail	XX/100
Security	pass/warn/fail	XX/100
URL Structure	pass/warn/fail	XX/100
Mobile	pass/warn/fail	XX/100
Core Web Vitals	pass/warn/fail	XX/100
Structured Data	pass/warn/fail	XX/100
JS Rendering	pass/warn/fail	XX/100
IndexNow	pass/warn/fail	XX/100

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-seo run pagespeed_check.py <url> --json for real PSI + CrUX field data (replaces lab-only CWV estimates), claude-seo run crux_history.py <url> --json for 25-week CWV trends, and claude-seo run gsc_inspect.py <url> --json for real indexation status per URL.

Error Handling

Scenario	Action
URL unreachable	Report connection error with status code. Suggest verifying URL, checking DNS resolution, and confirming the site is publicly accessible.
robots.txt not found	Note that no robots.txt was detected at the root domain. Recommend creating one with appropriate directives. Continue audit on remaining categories.
HTTPS not configured	Flag as a critical issue. Report whether HTTP is served without redirect, mixed content exists, or SSL certificate is missing/expired.
Core Web Vitals data unavailable	Note that CrUX data is not available (common for low-traffic sites). Suggest using Lighthouse lab data as a proxy and recommend increasing traffic before re-testing.

seo-technical

Technical SEO Audit

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