seo

これはレビュー時に保存された抜粋です。完全で最新の内容は外部ソースを確認してください。

---
name: seo
description: Optimize for search engine visibility and ranking. Use when asked to "improve SEO", "optimize for search", "fix meta tags", "add structured data", "sitemap optimization", or "search engine optimization".
license: MIT
metadata:
  author: web-quality-skills
  version: "1.0"
---

# SEO optimization

Search engine optimization based on Lighthouse SEO audits and Google Search guidelines. Focus on technical SEO, on-page optimization, and structured data.

## SEO fundamentals

Search ranking factors (approximate influence):

| Factor | Influence | This Skill |
|--------|-----------|------------|
| Content quality & relevance | ~40% | Partial (structure) |
| Backlinks & authority | ~25% | ✗ |
| Technical SEO | ~15% | ✓ |
| Page experience (Core Web Vitals) | ~10% | See [Core Web Vitals](../core-web-vitals/SKILL.md) |
| On-page SEO | ~10% | ✓ |

---

## Technical SEO

### Crawlability

**robots.txt:**
```text
# /robots.txt
User-agent: *
Allow: /

# Block admin/private areas
Disallow: /admin/
Disallow: /api/
Disallow: /private/

# Don't block resources needed for rendering
# ❌ Disallow: /static/

Sitemap: https://example.com/sitemap.xml
```

**Meta robots:**
```html
<!-- Default: indexable, followable -->
<meta name="robots" content="index, follow">

<!-- Noindex specific pages -->
<meta name="robots" content="noindex, nofollow">

<!-- Indexable but don't follow links -->
<meta name="robots" content="index, nofollow">

<!-- Control snippets -->
<meta name="robots" content="max-snippet:150, max-image-preview:large">
```

**Canonical URLs:**
```html
<!-- Prevent duplicate content issues -->
<link rel="canonical" href="https://example.com/page">

<!-- Self-referencing canonical (recommended) -->
<link rel="canonical" href="https://example.com/current-page">

<!-- For paginated content -->
<link rel="canonical" href="https://example.com/products">
<!-- Or use rel="prev" / rel="next" for explicit pagination -->
```

### XML sitemap

```xml
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://example.com/</loc>
    <lastmod>2024-01-15</lastmod>
    <changefreq>daily</changefreq>
    <priority>1.0</priority>
  </url>
  <url>
    <loc>https://example.com/products</loc>
    <lastmod>2024-01-14</lastmod>
    <changefreq>weekly</changefreq>
    <priority>0.8</priority>
  </url>
</urlset>
```

**Sitemap best practices:**
- Maximum 50,000 URLs or 50MB per sitemap
- Use sitemap index for larger sites
- Include only canonical, indexable URLs
- Update `lastmod` when content changes
- Submit to Google Search Console

### URL structure

```
✅ Good URLs:
https://example.com/products/blue-widget
https://example.com/blog/how-to-use-widgets

❌ Poor URLs:
https://example.com/p?id=12345
https://example.com/products/item/category/subcategory/blue-widget-2024-sale-discount
```

**URL guidelines:**
- Use hyphens, not underscores
- Lowercase only
- Keep short (< 75 characters)
- Include target keywords naturally
- Avoid parameters when possible
- Use HTTPS always

### HTTPS & security

```html
<!-- Ensure all resources use HTTPS -->
<img src="https://example.com/image.jpg">

<!-- Not: -->
<img src="http://example.com/image.jpg">
```

**Security headers for SEO trust signals:**
```
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
```

---

## On-page SEO

### Title tags

```html
<!-- ❌ Missing or generic -->
<title>Page</title>
<title>Home</title>

<!-- ✅ Descriptive with primary keyword -->
<title>Blue Widgets for Sale | Premium Quality | Example Store</title>
```

**Title tag guidelines:**
- 50-60 characters (Google truncates ~60)
- Primary keyword near the beginning
- Unique for every page
- Brand name at end (unless homepage)
- Action-oriented when appropriate

### Meta descriptions

```html
<!-- ❌ Missing or duplicate -->
<meta name="description" content="">

<!-- ✅ Compelling and unique -->
<met