| name | canon-seo |
| description | Use when auditing or implementing technical SEO — semantic HTML, meta tags, structured data, canonical URLs, sitemap, robots.txt, page speed as a ranking factor, and accessible content. Trigger when the user mentions SEO, search engine, meta tags, structured data, sitemap, or crawlability. |
CANON · SEO
Technical SEO is about making content findable and understandable by search engines. Not tricks — structure.
Semantic HTML is SEO
Search engines understand semantic HTML natively. Every rule in canon-accessibility that improves screen reader experience also improves SEO.
<h1> once per page, matching the page topic.- Heading hierarchy (h1 → h2 → h3) reflects content structure.
<nav>, <main>, <article>, <aside> help crawlers understand page layout.<a href> for links (not <div onClick>).<img alt> describes the image for image search.
Essential meta tags
<head>
<title>Page Title — Site Name</title>
<meta name="description" content="Concise summary under 155 characters.">
<link rel="canonical" href="https://example.com/page">
<meta name="robots" content="index, follow">
</head>
<title>: 50–60 characters. Unique per page. Primary keyword near the front.<meta description>: 120–155 characters. Compelling summary. Unique per page.<link rel="canonical">: prevents duplicate content penalties.<meta robots>: index, follow is default. noindex for admin pages.
Structured data (JSON-LD)
<script type="application/ld+json">
{
"@context": "https://schema.org",
"@type": "Article",
"headline": "Page Title",
"author": { "@type": "Person", "name": "Author" },
"datePublished": "2026-04-18"
}
</script>
Use for: articles, products, FAQs, breadcrumbs, organizations, events. Google uses structured data for rich results (stars, prices, FAQ dropdowns).
Page speed = ranking factor
Core Web Vitals are a Google ranking signal. See canon-performance for targets:
- LCP ≤ 2.5s
- INP ≤ 200ms
- CLS ≤ 0.1
Crawlability
robots.txt: allow crawlers access to important pages, block admin/API routes.sitemap.xml: list all public pages with <lastmod> dates.- Internal linking: every important page reachable within 3 clicks from the homepage.
- No orphan pages (pages with no internal links pointing to them).
Anti-patterns
| Anti-pattern | Why it fails |
|---|
Same <title> on every page | Search engines can't distinguish pages |
No <meta description> | Search engine generates one (often badly) |
| Keyword stuffing | Penalized by modern search engines |
| Client-rendered content without SSR/SSG | Crawlers may not execute JS |
| No canonical URL | Duplicate content across www/non-www, http/https |
| Blocking CSS/JS in robots.txt | Crawlers can't render the page |
Audit checklist
Sources
- Google Search Central · SEO starter guide
- Schema.org · structured data types
canon-performance for Core Web Vitalscanon-accessibility for semantic HTML
