Technical SEO Checklist for Developers (2026)

Technical SEO is the foundation. Without it, the best content is worthless. This checklist covers everything you need to know as a developer – with code examples you can implement directly.

1. Crawling & Indexing

robots.txt

Location: /robots.txt

User-agent: *
Allow: /

# Block admin and API routes
Disallow: /admin/
Disallow: /api/
Disallow: /_next/

# Sitemap location
Sitemap: https://example.com/sitemap.xml

Checklist:

robots.txt exists and is accessible
Important pages are not blocked
Sitemap location specified
API/Admin areas blocked

Test: site:yourdomain.com in Google – do you see all important pages?

XML Sitemap

Location: /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>2026-01-21</lastmod>
    <changefreq>weekly</changefreq>
    <priority>1.0</priority>
  </url>
  <url>
    <loc>https://example.com/blog/article-1</loc>
    <lastmod>2026-01-15</lastmod>
    <changefreq>monthly</changefreq>
    <priority>0.8</priority>
  </url>
</urlset>

For Next.js (auto-generate):

// next-sitemap.config.js
module.exports = {
  siteUrl: 'https://example.com',
  generateRobotsTxt: true,
  sitemapSize: 7000,
  changefreq: 'weekly',
  priority: 0.7,
  exclude: ['/admin/*', '/api/*'],
}

Checklist:

Sitemap contains all important URLs
lastmod dates are current
Sitemap submitted to Search Console
No 4xx/5xx URLs in sitemap

Canonical Tags

Avoid duplicate content:

<link rel="canonical" href="https://example.com/blog/article" />

Typical problems:

/blog/article vs /blog/article/
http:// vs https://
www. vs non-www
URL parameters (e.g., ?utm_source=...)

Next.js Example:

import Head from 'next/head';

export default function Page() {
  return (
    <Head>
      <link rel="canonical" href="https://example.com/page" />
    </Head>
  );
}

2. Core Web Vitals

LCP (Largest Contentful Paint)

Target: < 2.5 seconds

Common problems and solutions:

1. Optimize images:

<!-- Before -->
<img src="hero.jpg" />

<!-- After -->
<img
  src="hero.webp"
  srcset="hero-400.webp 400w, hero-800.webp 800w, hero-1200.webp 1200w"
  sizes="(max-width: 400px) 400px, (max-width: 800px) 800px, 1200px"
  loading="eager"
  fetchpriority="high"
  alt="Hero Image"
/>

2. Preload critical resources:

<link rel="preload" href="/fonts/main.woff2" as="font" type="font/woff2" crossorigin>
<link rel="preload" href="/hero.webp" as="image">

3. Server Response Time:

Use CDN
Implement caching
Server-Side Rendering for critical content

FID/INP (First Input Delay / Interaction to Next Paint)

Target: < 100ms (FID), < 200ms (INP)

Main problem: JavaScript blocks the main thread

Solutions:

1. Code Splitting:

// Dynamic import
const HeavyComponent = dynamic(() => import('./HeavyComponent'), {
  loading: () => <Skeleton />,
});

2. Web Workers for heavy calculations:

// worker.js
self.onmessage = function(e) {
  const result = heavyCalculation(e.data);
  self.postMessage(result);
};

// main.js
const worker = new Worker('worker.js');
worker.postMessage(data);
worker.onmessage = (e) => console.log(e.data);

3. Debounce and Throttle:

const handleScroll = throttle(() => {
  // Expensive operation
}, 100);

CLS (Cumulative Layout Shift)

Target: < 0.1

Main problems and solutions:

1. Images without dimensions:

<!-- Bad -->
<img src="photo.jpg" />

<!-- Good -->
<img src="photo.jpg" width="800" height="600" />

<!-- Or with aspect-ratio -->
<img src="photo.jpg" style="aspect-ratio: 4/3; width: 100%;" />

2. Ads and Embeds:

.ad-container {
  min-height: 250px; /* Reserve space */
}

3. Web Fonts:

@font-face {
  font-family: 'CustomFont';
  src: url('/font.woff2') format('woff2');
  font-display: swap; /* or optional */
  size-adjust: 100%;
  ascent-override: 95%;
  descent-override: 20%;
}

3. Structured Data (Schema Markup)

Article Schema

{
  "@context": "https://schema.org",
  "@type": "Article",
  "headline": "Technical SEO Checklist for Developers",
  "description": "Everything developers need to know about technical SEO",
  "author": {
    "@type": "Person",
    "name": "Jonas Höttler",
    "url": "https://hoettler.com"
  },
  "datePublished": "2026-06-30",
  "dateModified": "2026-06-30",
  "publisher": {
    "@type": "Organization",
    "name": "Höttler Tech",
    "logo": {
      "@type": "ImageObject",
      "url": "https://hoettler.com/logo.png"
    }
  },
  "image": "https://hoettler.com/article-image.jpg"
}

FAQ Schema

{
  "@context": "https://schema.org",
  "@type": "FAQPage",
  "mainEntity": [
    {
      "@type": "Question",
      "name": "What is technical SEO?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Technical SEO encompasses all technical optimizations..."
      }
    }
  ]
}

HowTo Schema

Perfect for tutorials:

{
  "@context": "https://schema.org",
  "@type": "HowTo",
  "name": "How to improve Core Web Vitals",
  "step": [
    {
      "@type": "HowToStep",
      "name": "Optimize images",
      "text": "Convert images to WebP and use responsive images."
    }
  ]
}

Implementation in Next.js:

export default function Article({ data }) {
  const jsonLd = {
    "@context": "https://schema.org",
    "@type": "Article",
    headline: data.title,
    // ...
  };

  return (
    <>
      <script
        type="application/ld+json"
        dangerouslySetInnerHTML={{ __html: JSON.stringify(jsonLd) }}
      />
      {/* Article content */}
    </>
  );
}

4. Mobile Optimization

Viewport Meta Tag

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

Mobile-First CSS

/* Base styles (mobile) */
.container {
  padding: 1rem;
}

/* Tablet */
@media (min-width: 768px) {
  .container {
    padding: 2rem;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  .container {
    padding: 3rem;
    max-width: 1200px;
  }
}

Touch Targets

button, a {
  min-height: 48px;
  min-width: 48px;
  padding: 12px;
}

5. HTTPS & Security

HSTS Header

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

In Next.js (next.config.js):

module.exports = {
  async headers() {
    return [
      {
        source: '/:path*',
        headers: [
          {
            key: 'Strict-Transport-Security',
            value: 'max-age=31536000; includeSubDomains'
          }
        ]
      }
    ]
  }
}

Content Security Policy

Content-Security-Policy: default-src 'self'; script-src 'self' 'unsafe-inline' https://www.googletagmanager.com; style-src 'self' 'unsafe-inline';

6. Internationalization (i18n)

hreflang Tags

<link rel="alternate" hreflang="de" href="https://example.com/de/page" />
<link rel="alternate" hreflang="en" href="https://example.com/en/page" />
<link rel="alternate" hreflang="x-default" href="https://example.com/en/page" />

In the Sitemap

<url>
  <loc>https://example.com/de/page</loc>
  <xhtml:link rel="alternate" hreflang="de" href="https://example.com/de/page"/>
  <xhtml:link rel="alternate" hreflang="en" href="https://example.com/en/page"/>
</url>

7. Performance Optimization

Resource Hints

<!-- DNS Prefetch for external domains -->
<link rel="dns-prefetch" href="//fonts.googleapis.com">

<!-- Preconnect for critical domains -->
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>

<!-- Preload for critical resources -->
<link rel="preload" href="/critical.css" as="style">

<!-- Prefetch for likely needed resources -->
<link rel="prefetch" href="/next-page.js">

Lazy Loading

<!-- Native Lazy Loading -->
<img src="image.jpg" loading="lazy" alt="...">

<!-- Intersection Observer for complex cases -->
<script>
const observer = new IntersectionObserver((entries) => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      entry.target.src = entry.target.dataset.src;
      observer.unobserve(entry.target);
    }
  });
});

document.querySelectorAll('img[data-src]').forEach(img => observer.observe(img));
</script>

The Ultimate Checklist

Crawling & Indexing

robots.txt correctly configured
XML Sitemap present and current
Sitemap submitted to Search Console
Canonical tags on all pages
No duplicate content issues

Core Web Vitals

Structured Data

Article Schema on blog posts
FAQ Schema where relevant
Organization Schema on homepage
Schema validated (Rich Results Test)

Mobile

Viewport Meta Tag present
Mobile-responsive design
Touch targets minimum 48x48px
No horizontal scrollbars

Security

HTTPS everywhere
HSTS header set
Mixed content avoided

Internationalization

hreflang tags correct
Language specified in HTML tag
Language versions in sitemap

Tools for Verification

Tool	Checks	Link
Google Search Console	Indexing, errors	search.google.com/search-console
PageSpeed Insights	Core Web Vitals	pagespeed.web.dev
Rich Results Test	Structured Data	search.google.com/test/rich-results
Mobile-Friendly Test	Mobile optimization	search.google.com/test/mobile-friendly
Lighthouse	Everything	In Chrome DevTools

Conclusion

Technical SEO is not a one-time project – it's continuous work. But once set up correctly, it forms the foundation for all further SEO measures.

The most important priorities:

Be crawlable – robots.txt, sitemap, no blockers
Be fast – optimize Core Web Vitals
Be structured – implement Schema Markup
Mobile-first – responsive, touch-friendly

Use the checklist as a starting point and work through it systematically.

Want to learn more about keyword research without expensive tools? Our guide SEO for Tech Blogs shows you free methods.

Technical SEO is the foundation. Without it, the best content is worthless. This checklist covers everything you need to know as a developer – with code examples you can implement directly.

1. Crawling & Indexing

robots.txt

Location: /robots.txt

User-agent: *
Allow: /

# Block admin and API routes
Disallow: /admin/
Disallow: /api/
Disallow: /_next/

# Sitemap location
Sitemap: https://example.com/sitemap.xml

Checklist:

robots.txt exists and is accessible
Important pages are not blocked
Sitemap location specified
API/Admin areas blocked

Test: site:yourdomain.com in Google – do you see all important pages?

XML Sitemap

Location: /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>2026-01-21</lastmod>
    <changefreq>weekly</changefreq>
    <priority>1.0</priority>
  </url>
  <url>
    <loc>https://example.com/blog/article-1</loc>
    <lastmod>2026-01-15</lastmod>
    <changefreq>monthly</changefreq>
    <priority>0.8</priority>
  </url>
</urlset>

For Next.js (auto-generate):

// next-sitemap.config.js
module.exports = {
  siteUrl: 'https://example.com',
  generateRobotsTxt: true,
  sitemapSize: 7000,
  changefreq: 'weekly',
  priority: 0.7,
  exclude: ['/admin/*', '/api/*'],
}

Checklist:

Sitemap contains all important URLs
lastmod dates are current
Sitemap submitted to Search Console
No 4xx/5xx URLs in sitemap

Canonical Tags

Avoid duplicate content:

<link rel="canonical" href="https://example.com/blog/article" />

Typical problems:

/blog/article vs /blog/article/
http:// vs https://
www. vs non-www
URL parameters (e.g., ?utm_source=...)

Next.js Example:

import Head from 'next/head';

export default function Page() {
  return (
    <Head>
      <link rel="canonical" href="https://example.com/page" />
    </Head>
  );
}

2. Core Web Vitals

LCP (Largest Contentful Paint)

Target: < 2.5 seconds

Common problems and solutions:

1. Optimize images:

<!-- Before -->
<img src="hero.jpg" />

<!-- After -->
<img
  src="hero.webp"
  srcset="hero-400.webp 400w, hero-800.webp 800w, hero-1200.webp 1200w"
  sizes="(max-width: 400px) 400px, (max-width: 800px) 800px, 1200px"
  loading="eager"
  fetchpriority="high"
  alt="Hero Image"
/>

2. Preload critical resources:

<link rel="preload" href="/fonts/main.woff2" as="font" type="font/woff2" crossorigin>
<link rel="preload" href="/hero.webp" as="image">

3. Server Response Time:

Use CDN
Implement caching
Server-Side Rendering for critical content

FID/INP (First Input Delay / Interaction to Next Paint)

Target: < 100ms (FID), < 200ms (INP)

Main problem: JavaScript blocks the main thread

Solutions:

1. Code Splitting:

// Dynamic import
const HeavyComponent = dynamic(() => import('./HeavyComponent'), {
  loading: () => <Skeleton />,
});

2. Web Workers for heavy calculations:

// worker.js
self.onmessage = function(e) {
  const result = heavyCalculation(e.data);
  self.postMessage(result);
};

// main.js
const worker = new Worker('worker.js');
worker.postMessage(data);
worker.onmessage = (e) => console.log(e.data);

3. Debounce and Throttle:

const handleScroll = throttle(() => {
  // Expensive operation
}, 100);

CLS (Cumulative Layout Shift)

Target: < 0.1

Main problems and solutions:

1. Images without dimensions:

<!-- Bad -->
<img src="photo.jpg" />

<!-- Good -->
<img src="photo.jpg" width="800" height="600" />

<!-- Or with aspect-ratio -->
<img src="photo.jpg" style="aspect-ratio: 4/3; width: 100%;" />

2. Ads and Embeds:

.ad-container {
  min-height: 250px; /* Reserve space */
}

3. Web Fonts:

@font-face {
  font-family: 'CustomFont';
  src: url('/font.woff2') format('woff2');
  font-display: swap; /* or optional */
  size-adjust: 100%;
  ascent-override: 95%;
  descent-override: 20%;
}

3. Structured Data (Schema Markup)

Article Schema

{
  "@context": "https://schema.org",
  "@type": "Article",
  "headline": "Technical SEO Checklist for Developers",
  "description": "Everything developers need to know about technical SEO",
  "author": {
    "@type": "Person",
    "name": "Jonas Höttler",
    "url": "https://hoettler.com"
  },
  "datePublished": "2026-06-30",
  "dateModified": "2026-06-30",
  "publisher": {
    "@type": "Organization",
    "name": "Höttler Tech",
    "logo": {
      "@type": "ImageObject",
      "url": "https://hoettler.com/logo.png"
    }
  },
  "image": "https://hoettler.com/article-image.jpg"
}

FAQ Schema

{
  "@context": "https://schema.org",
  "@type": "FAQPage",
  "mainEntity": [
    {
      "@type": "Question",
      "name": "What is technical SEO?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Technical SEO encompasses all technical optimizations..."
      }
    }
  ]
}

HowTo Schema

Perfect for tutorials:

{
  "@context": "https://schema.org",
  "@type": "HowTo",
  "name": "How to improve Core Web Vitals",
  "step": [
    {
      "@type": "HowToStep",
      "name": "Optimize images",
      "text": "Convert images to WebP and use responsive images."
    }
  ]
}

Implementation in Next.js:

export default function Article({ data }) {
  const jsonLd = {
    "@context": "https://schema.org",
    "@type": "Article",
    headline: data.title,
    // ...
  };

  return (
    <>
      <script
        type="application/ld+json"
        dangerouslySetInnerHTML={{ __html: JSON.stringify(jsonLd) }}
      />
      {/* Article content */}
    </>
  );
}

4. Mobile Optimization

Viewport Meta Tag

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

Mobile-First CSS

/* Base styles (mobile) */
.container {
  padding: 1rem;
}

/* Tablet */
@media (min-width: 768px) {
  .container {
    padding: 2rem;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  .container {
    padding: 3rem;
    max-width: 1200px;
  }
}

Touch Targets

button, a {
  min-height: 48px;
  min-width: 48px;
  padding: 12px;
}

5. HTTPS & Security

HSTS Header

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

In Next.js (next.config.js):

module.exports = {
  async headers() {
    return [
      {
        source: '/:path*',
        headers: [
          {
            key: 'Strict-Transport-Security',
            value: 'max-age=31536000; includeSubDomains'
          }
        ]
      }
    ]
  }
}

Content Security Policy

Content-Security-Policy: default-src 'self'; script-src 'self' 'unsafe-inline' https://www.googletagmanager.com; style-src 'self' 'unsafe-inline';

6. Internationalization (i18n)

hreflang Tags

<link rel="alternate" hreflang="de" href="https://example.com/de/page" />
<link rel="alternate" hreflang="en" href="https://example.com/en/page" />
<link rel="alternate" hreflang="x-default" href="https://example.com/en/page" />

In the Sitemap

<url>
  <loc>https://example.com/de/page</loc>
  <xhtml:link rel="alternate" hreflang="de" href="https://example.com/de/page"/>
  <xhtml:link rel="alternate" hreflang="en" href="https://example.com/en/page"/>
</url>

7. Performance Optimization

Resource Hints

<!-- DNS Prefetch for external domains -->
<link rel="dns-prefetch" href="//fonts.googleapis.com">

<!-- Preconnect for critical domains -->
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>

<!-- Preload for critical resources -->
<link rel="preload" href="/critical.css" as="style">

<!-- Prefetch for likely needed resources -->
<link rel="prefetch" href="/next-page.js">

Lazy Loading

<!-- Native Lazy Loading -->
<img src="image.jpg" loading="lazy" alt="...">

<!-- Intersection Observer for complex cases -->
<script>
const observer = new IntersectionObserver((entries) => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      entry.target.src = entry.target.dataset.src;
      observer.unobserve(entry.target);
    }
  });
});

document.querySelectorAll('img[data-src]').forEach(img => observer.observe(img));
</script>

The Ultimate Checklist

Crawling & Indexing

robots.txt correctly configured
XML Sitemap present and current
Sitemap submitted to Search Console
Canonical tags on all pages
No duplicate content issues

Core Web Vitals

Structured Data

Article Schema on blog posts
FAQ Schema where relevant
Organization Schema on homepage
Schema validated (Rich Results Test)

Mobile

Viewport Meta Tag present
Mobile-responsive design
Touch targets minimum 48x48px
No horizontal scrollbars

Security

HTTPS everywhere
HSTS header set
Mixed content avoided

Internationalization

hreflang tags correct
Language specified in HTML tag
Language versions in sitemap

Tools for Verification

Tool	Checks	Link
Google Search Console	Indexing, errors	search.google.com/search-console
PageSpeed Insights	Core Web Vitals	pagespeed.web.dev
Rich Results Test	Structured Data	search.google.com/test/rich-results
Mobile-Friendly Test	Mobile optimization	search.google.com/test/mobile-friendly
Lighthouse	Everything	In Chrome DevTools

Conclusion

Technical SEO is not a one-time project – it's continuous work. But once set up correctly, it forms the foundation for all further SEO measures.

The most important priorities:

Be crawlable – robots.txt, sitemap, no blockers
Be fast – optimize Core Web Vitals
Be structured – implement Schema Markup
Mobile-first – responsive, touch-friendly

Use the checklist as a starting point and work through it systematically.

Want to learn more about keyword research without expensive tools? Our guide SEO for Tech Blogs shows you free methods.

1. Crawling & Indexing

robots.txt

XML Sitemap

Canonical Tags

2. Core Web Vitals

LCP (Largest Contentful Paint)

FID/INP (First Input Delay / Interaction to Next Paint)

CLS (Cumulative Layout Shift)

3. Structured Data (Schema Markup)

Article Schema

FAQ Schema

HowTo Schema

4. Mobile Optimization

Viewport Meta Tag

Mobile-First CSS

Touch Targets

5. HTTPS & Security

HSTS Header

Content Security Policy

6. Internationalization (i18n)

hreflang Tags

In the Sitemap

7. Performance Optimization

Resource Hints

Lazy Loading

The Ultimate Checklist

Crawling & Indexing

Core Web Vitals

Structured Data

Mobile

Security

Internationalization

Tools for Verification

Conclusion

Related Articles

Pricing Psychology for SaaS: Why Customers Pay What They Pay

Jobs to Be Done: Understand Why Customers Really Buy

SEO for Tech Blogs: Finding Keywords Without Expensive Tools

Have a similar project?

1. Crawling & Indexing

robots.txt

XML Sitemap

Canonical Tags

2. Core Web Vitals

LCP (Largest Contentful Paint)

FID/INP (First Input Delay / Interaction to Next Paint)

CLS (Cumulative Layout Shift)

3. Structured Data (Schema Markup)

Article Schema

FAQ Schema

HowTo Schema

4. Mobile Optimization

Viewport Meta Tag

Mobile-First CSS

Touch Targets

5. HTTPS & Security

HSTS Header

Content Security Policy

6. Internationalization (i18n)

hreflang Tags

In the Sitemap

7. Performance Optimization

Resource Hints

Lazy Loading

The Ultimate Checklist

Crawling & Indexing

Core Web Vitals

Structured Data

Mobile

Security

Internationalization

Tools for Verification

Conclusion

Related Articles

Pricing Psychology for SaaS: Why Customers Pay What They Pay

Jobs to Be Done: Understand Why Customers Really Buy

SEO for Tech Blogs: Finding Keywords Without Expensive Tools

Have a similar project?