seo-technical

Technical SEO Audit

When to Use

• Use when the user wants a technical SEO review focused on crawlability, indexability, performance, or rendering.
• Use when auditing robots.txt, canonicalization, JavaScript SEO, Core Web Vitals, or AI crawler access.
• Use when the task is infrastructure- and implementation-oriented rather than content-focused.

Categories

1. Crawlability

• robots.txt: exists, valid, not blocking important resources
• XML sitemap: exists, referenced in robots.txt, valid format
• 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

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 full AI visibility optimization.

2. Indexability

• Canonical tags: self-referencing, no conflicts with noindex
• Duplicate content: near-duplicates, parameter URLs, www vs non-www
• 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

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

• 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: Google indexes mobile version. Mobile-first indexing is 100% complete as of July 5, 2024. Google now crawls and indexes ALL websites exclusively with the mobile Googlebot user-agent.

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 fully removed from all Chrome tools (CrUX API, PageSpeed Insights, Lighthouse) on September 9, 2024. 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:

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

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.

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. |

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.