Technical SEO
Audit and fix the layer beneath the content: how search engines crawl, render, index, and trust a site. Stack-agnostic.
When to use
- Site-wide audit before or after a migration
- Investigating indexing or ranking drops
- Setting up SEO foundations on a new site
- Auditing Core Web Vitals or page experience signals
- Fixing crawl waste, redirect chains, or canonical issues
- Setting up multilingual or multi-regional sites
When NOT to use
- Single-page on-page optimization (use
seo-onpage) - Keyword strategy or content planning (use
seo-keyword) - Competitor backlink or SERP analysis (use
seo-competitor) - Pure performance optimization without SEO context (use
performance-optimization)
Required inputs
- The site URL or staging URL
- Access to (at minimum) view the rendered HTML, robots.txt, and sitemap
- Ideally: search console access, server logs, and a crawler
If the site is large (10K+ URLs), confirm whether the audit is a full crawl or a sample.
The framework: 6 layers
Technical SEO has six layers, stacked. A failure in a lower layer breaks everything above it.
1. Crawlability
Can search engines access the URLs?
- robots.txt does not block important paths
- No accidental
noindexon indexable pages - No accidental
disallowpatterns blocking CSS or JS (rendering breaks) - Sitemap is present, returns 200, and lists canonical URLs only
- Sitemap is referenced in robots.txt
- No infinite spaces (faceted nav generating endless URLs)
- Crawl budget is not wasted on low-value URLs
2. Indexability
Of crawlable URLs, which should be indexed?
- One canonical URL per piece of content (no duplicates)
- Canonical tags self-reference on canonical pages
noindexon staging, search results, filter pages, thank-you pages, internal admin- No mixed signals (canonical pointing one way, sitemap another, internal links a third)
- Pagination handled correctly (rel=next/prev is deprecated, but consistent canonicals matter)
- Parameter handling deliberate (UTM, session IDs, sort orders)
3. Rendering
Does the rendered HTML match what crawlers see?
- Critical content visible without JavaScript (or properly server-rendered)
- For SPAs: confirm Googlebot sees the rendered content (test with the URL Inspection tool)
- No cloaking (showing different content to bots vs users)
- Lazy-loaded content has proper loading attributes
- Hydration errors do not strip content from the rendered DOM
4. Site architecture
Is the site structured for both users and crawlers?
- Clear URL hierarchy that mirrors site structure
- Important pages reachable in 3 clicks or fewer from the homepage
- Internal linking distributes authority logically
- Breadcrumb navigation present and marked up with schema
- No orphan pages (pages with no internal links)
- No redirect chains (one redirect max)
- No 4xx errors on internally-linked URLs
5. Structured data and signals
Does the site speak crawler language?
- Schema.org markup on appropriate page types
- JSON-LD format (preferred over microdata)
- Validates in the Rich Results Test
- Organization or LocalBusiness schema on the homepage or about page
- BreadcrumbList schema on nested pages
- Author and publisher schema linked correctly on content pages
- llms.txt present at the root (for AI crawlers, see
seo-aeo-geo)
6. Page experience and security
Does the site meet the page experience baseline?
- HTTPS on all pages, no mixed content
- HSTS header set
- Core Web Vitals pass (LCP, INP, CLS within thresholds)
- Mobile-friendly (responsive, no horizontal scroll, tap targets sized correctly)
- No intrusive interstitials on mobile
- Stable URL structure (no random URL changes between deploys)
- 404 pages return 404, not 200 with "page not found" content (soft 404)
Workflow
- Define scope. Whole site, a subfolder, a migration check, or a specific issue.
- Confirm access. What can you actually see (HTML, robots, sitemap, search console, server logs, staging)?
- Crawl. Use a crawler to enumerate URLs and statuses. Sample if the site is huge.
- Run the 6-layer framework. Score each, note specific issues with example URLs.
- Cross-reference. Search console for what's actually indexed. Compare to sitemap and crawl output.
- Prioritize. Critical (blocks indexing or causes traffic loss), Important (suboptimal), Nice-to-have (polish).
- Write the report. Use the template in
references/audit-template.md.
Failure patterns
- Optimizing rankings on a page that is
noindex. Always check indexability before content work. - Adding sitemaps without fixing canonical issues. A sitemap of duplicate URLs is worse than no sitemap.
- Blocking crawlers from CSS or JS. Breaks Google's rendering. Common in over-aggressive robots.txt files.
- Over-relying on canonical tags. Canonicals are hints, not directives. Use redirects when content actually moved.
- Migrating without a redirect map. Single biggest cause of post-migration traffic loss.
- Treating Core Web Vitals as the only ranking signal. Page experience matters but does not override relevance.
Output format
Default output is a markdown audit at seo-technical-audit.md. Structure:
- Scope and methodology
- Executive summary (3 to 5 critical findings)
- 6-layer score
- Critical issues (with example URLs)
- Important issues
- Nice-to-have polish
- Implementation roadmap (sequenced)
For migrations, include a redirect map as a CSV alongside the report.
If required data is unavailable
This skill's output depends on data, measurements, or tool results it cannot generate on its own. When a required input, tool, or data source is unavailable or unverifiable, the sanctioned output is the deliverable with the gap stated: what was needed, what was actually obtained or verified, and which parts of the output are affected. Fabricating, estimating, or interpolating a required number to complete the deliverable is never sanctioned. A stated gap is a complete answer.
Reference files
references/audit-template.md- Fillable technical SEO audit template.references/migration-checklist.md- Pre and post-migration checklist (covers the highest-risk scenario).
