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
On-page SEO	~10%	✓

---

Technical SEO

Crawlability

robots.txt:

# /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:

<!-- 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:

<!-- 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 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

<!-- 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

<!-- ❌ 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

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

<!-- ✅ Compelling and unique -->
<meta
  name="description"
  content="Shop premium blue widgets with free shipping. 30-day returns. Rated 4.9/5 by 10,000+ customers. Order today and save 20%."
/>

Meta description guidelines:

• 150-160 characters
• Include primary keyword naturally
• Compelling call-to-action
• Unique for every page
• Matches page content

Heading structure

<!-- ❌ Poor structure -->
<h2>Welcome to Our Store</h2>
<h4>Products</h4>
<h1>Contact Us</h1>

<!-- ✅ Proper hierarchy -->
<h1>Blue Widgets - Premium Quality</h1>
<h2>Product Features</h2>
<h3>Durability</h3>
<h3>Design</h3>
<h2>Customer Reviews</h2>
<h2>Pricing</h2>

Heading guidelines:

• Single <h1> per page (the main topic)
• Logical hierarchy (don't skip levels)
• Include keywords naturally
• Descriptive, not generic

Image SEO

<!-- ❌ Poor image SEO -->
<img src="IMG_12345.jpg" />

<!-- ✅ Optimized image -->
<img
  src="blue-widget-product-photo.webp"
  alt="Blue widget with chrome finish, side view showing control panel"
  width="800"
  height="600"
  loading="lazy"
/>

Image guidelines:

• Descriptive filenames with keywords
• Alt text describes the image content
• Compressed and properly sized
• WebP/AVIF with fallbacks
• Lazy load below-fold images

Internal linking

<!-- ❌ Non-descriptive -->
<a href="/products">Click here</a>
<a href="/widgets">Read more</a>

<!-- ✅ Descriptive anchor text -->
<a href="/products/blue-widgets">Browse our blue widget collection</a>
<a href="/guides/widget-maintenance">Learn how to maintain your widgets</a>

Linking guidelines:

• Descriptive anchor text with keywords
• Link to relevant internal pages
• Reasonable number of links per page
• Fix broken links promptly
• Use breadcrumbs for hierarchy

---

Structured data (JSON-LD)

Organization

<script type="application/ld+json">
  {
    "@context": "https://schema.org",
    "@type": "Organization",
    "name": "Example Company",
    "url": "https://example.com",
    "logo": "https://example.com/logo.png",
    "sameAs": ["https://twitter.com/example", "https://linkedin.com/company/example"],
    "contactPoint": {
      "@type": "ContactPoint",
      "telephone": "+1-555-123-4567",
      "contactType": "customer service"
    }
  }
</script>

Article

<script type="application/ld+json">
  {
    "@context": "https://schema.org",
    "@type": "Article",
    "headline": "How to Choose the Right Widget",
    "description": "Complete guide to selecting widgets for your needs.",
    "image": "https://example.com/article-image.jpg",
    "author": {
      "@type": "Person",
      "name": "Jane Smith",
      "url": "https://example.com/authors/jane-smith"
    },
    "publisher": {
      "@type": "Organization",
      "name": "Example Blog",
      "logo": {
        "@type": "ImageObject",
        "url": "https://example.com/logo.png"
      }
    },
    "datePublished": "2024-01-15",
    "dateModified": "2024-01-20"
  }
</script>

Product

<script type="application/ld+json">
  {
    "@context": "https://schema.org",
    "@type": "Product",
    "name": "Blue Widget Pro",
    "image": "https://example.com/blue-widget.jpg",
    "description": "Premium blue widget with advanced features.",
    "brand": {
      "@type": "Brand",
      "name": "WidgetCo"
    },
    "offers": {
      "@type": "Offer",
      "price": "49.99",
      "priceCurrency": "USD",
      "availability": "https://schema.org/InStock",
      "url": "https://example.com/products/blue-widget"
    },
    "aggregateRating": {
      "@type": "AggregateRating",
      "ratingValue": "4.8",
      "reviewCount": "1250"
    }
  }
</script>

FAQ

<script type="application/ld+json">
  {
    "@context": "https://schema.org",
    "@type": "FAQPage",
    "mainEntity": [
      {
        "@type": "Question",
        "name": "What colors are available?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "Our widgets come in blue, red, and green."
        }
      },
      {
        "@type": "Question",
        "name": "What is the warranty?",
        "acceptedAnswer": {
          "@type": "Answer",
          "text": "All widgets include a 2-year warranty."
        }
      }
    ]
  }
</script>

Breadcrumbs

<script type="application/ld+json">
  {
    "@context": "https://schema.org",
    "@type": "BreadcrumbList",
    "itemListElement": [
      {
        "@type": "ListItem",
        "position": 1,
        "name": "Home",
        "item": "https://example.com"
      },
      {
        "@type": "ListItem",
        "position": 2,
        "name": "Products",
        "item": "https://example.com/products"
      },
      {
        "@type": "ListItem",
        "position": 3,
        "name": "Blue Widgets",
        "item": "https://example.com/products/blue-widgets"
      }
    ]
  }
</script>

Validation

Test structured data at:

• Google Rich Results Test
• Schema.org Validator

---

Mobile SEO

Responsive design

<!-- ❌ Not mobile-friendly -->
<meta name="viewport" content="width=1024" />

<!-- ✅ Responsive viewport -->
<meta name="viewport" content="width=device-width, initial-scale=1" />

Tap targets

/* ❌ Too small for mobile */
.small-link {
  padding: 4px;
  font-size: 12px;
}

/* ✅ Adequate tap target */
.mobile-friendly-link {
  padding: 12px;
  font-size: 16px;
  min-height: 48px;
  min-width: 48px;
}

Font sizes

/* ❌ Too small on mobile */
body {
  font-size: 10px;
}

/* ✅ Readable without zooming */
body {
  font-size: 16px;
  line-height: 1.5;
}

---

International SEO

Hreflang tags

<!-- For multi-language sites -->
<link rel="alternate" hreflang="en" href="https://example.com/page" />
<link rel="alternate" hreflang="es" href="https://example.com/es/page" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />
<link rel="alternate" hreflang="x-default" href="https://example.com/page" />

Language declaration

<html lang="en">
  <!-- or -->
  <html lang="es-MX"></html>
</html>

---

SEO audit checklist

Critical

• HTTPS enabled
• robots.txt allows crawling
• No noindex on important pages
• Title tags present and unique
• Single <h1> per page

High priority

• Meta descriptions present
• Sitemap submitted
• Canonical URLs set
• Mobile-responsive
• Core Web Vitals passing

Medium priority

• Structured data implemented
• Internal linking strategy
• Image alt text
• Descriptive URLs
• Breadcrumb navigation

Ongoing

• Fix crawl errors in Search Console
• Update sitemap when content changes
• Monitor ranking changes
• Check for broken links
• Review Search Console insights

---

Tools

Tool	Use
Google Search Console	Monitor indexing, fix issues
Google PageSpeed Insights	Performance + Core Web Vitals
Rich Results Test	Validate structured data
Lighthouse	Full SEO audit
Screaming Frog	Crawl analysis

References

• Google Search Central
• Schema.org
• Core Web Vitals
• Web Quality Audit