Technical SEO Checklist 2026: 10 Critical Checks You Can't Ignore

Technical SEO is the foundation everything else sits on. You can write brilliant content and build perfect backlinks, but if search engines cannot crawl, render, or index your pages correctly, none of it matters.

This checklist covers 10 technical checks that every website should pass. Each one takes minutes to fix but can cost you significant traffic if ignored.

1. SSL/HTTPS

Google has treated HTTPS as a ranking signal since 2014. In 2026, running HTTP is essentially disqualifying your site from serious rankings.

What to check:

• Valid SSL certificate (not expired, not self-signed)
• All pages serve over HTTPS
• HTTP requests redirect to HTTPS (301, not 302)
• No mixed content warnings (HTTP resources loaded on HTTPS pages)

Fix: Get a free certificate from Let's Encrypt. Most hosting providers offer one-click SSL setup.

2. robots.txt

Your robots.txt file tells crawlers which parts of your site to access. A misconfigured file can accidentally block your entire site from indexing.

What to check:

• File exists at /robots.txt and returns 200
• No accidental Disallow: / blocking the whole site
• CSS and JS files are not blocked (Googlebot needs them for rendering)
• Sitemap URL is referenced

Fix: Start simple. Allow everything except admin and private paths. Always include a Sitemap: directive.

3. XML Sitemap

A sitemap helps search engines discover and prioritize your pages. Sites with thousands of pages absolutely need one; smaller sites benefit too.

What to check:

• Sitemap exists at /sitemap.xml or the location specified in robots.txt
• All listed URLs return 200 (no 404s or redirects)
• Sitemap is not larger than 50MB or 50,000 URLs
• <lastmod> dates are accurate (not all set to today)

Fix: Use your CMS sitemap plugin or generate one with a tool like Yoast, Screaming Frog, or a static site generator.

4. Mobile-Friendliness

Google uses mobile-first indexing. Your mobile experience is your primary experience for ranking purposes.

What to check:

• Viewport meta tag is present: <meta name="viewport" content="width=device-width, initial-scale=1">
• Text is readable without zooming
• Tap targets (buttons, links) are at least 48x48px with enough spacing
• No horizontal scrolling

Fix: Use responsive CSS. Test on actual devices, not just browser DevTools.

5. Favicon

A missing favicon triggers 404 errors on every page load, creates a poor user experience in browser tabs, and looks unprofessional in search results.

What to check:

• Favicon exists and loads correctly
• Both /favicon.ico and <link rel="icon"> are set
• Multiple sizes provided for different devices

Fix: Create a 32x32 ICO file at minimum. Use a favicon generator for all modern formats (SVG, Apple Touch Icon, etc.).

6. WWW Redirect

Your site should resolve to exactly one canonical domain. Both www.example.com and example.com should work, but one must redirect to the other.

What to check:

• Pick either www or non-www and stick with it
• The non-canonical version 301-redirects to the canonical one
• All internal links use the canonical version

Fix: Set up a 301 redirect in your server config (nginx, Apache) or DNS-level redirect.

7. HTTP Headers

Security and caching headers protect your users and improve performance. Search engines also factor some security signals into rankings.

What to check:

• Strict-Transport-Security (HSTS) — forces HTTPS
• X-Content-Type-Options: nosniff — prevents MIME sniffing
• X-Frame-Options — prevents clickjacking
• Content-Security-Policy — controls resource loading
• Cache headers (Cache-Control, ETag) for static assets

Fix: Add security headers in your web server or CDN configuration. Use securityheaders.com to test.

8. Site Infrastructure

Behind-the-scenes configuration issues can silently hurt your SEO.

What to check:

• Service pages (404, login, cart) have noindex meta tags
• Robots.txt coverage matches your actual site structure
• Sitemap URLs are consistent with canonical URLs
• No orphan pages (pages not linked from anywhere)

Fix: Audit your site structure quarterly. Use crawl tools to find disconnected or misconfigured pages.

9. Core Web Vitals

Google measures real-user performance via three metrics: LCP (Largest Contentful Paint), INP (Interaction to Next Paint), and CLS (Cumulative Layout Shift).

What to check:

• LCP under 2.5 seconds
• INP under 200 milliseconds
• CLS under 0.1
• No render-blocking resources delaying first paint

Fix: Optimize images (WebP, proper sizing), defer non-critical JavaScript, set explicit dimensions on images and ads, and use a CDN.

10. IndexNow

IndexNow lets you notify search engines (Bing, Yandex) about content changes instantly instead of waiting for a crawl.

What to check:

• IndexNow API key is configured
• Ownership verification file exists at /{key}.txt
• New and updated pages trigger IndexNow pings

Fix: Generate an IndexNow key, host the verification file, and integrate the API call into your publishing workflow.

Run All 10 in 30 Seconds

You could check each of these manually. Or you could enter your URL once and get all 10 checked automatically with a scored report.

Run your free technical SEO audit at CheckSEO.

References

• Google — HTTPS as a ranking signal (2014)
• Google — Introduction to robots.txt
• Google — Sitemaps overview
• Google — Mobile-first indexing best practices
• web.dev — Web Vitals: essential metrics
• web.dev — Largest Contentful Paint (LCP)
• web.dev — Interaction to Next Paint (INP)
• web.dev — Cumulative Layout Shift (CLS)
• Google — Core Web Vitals and search
• IndexNow — IndexNow protocol
• Let's Encrypt — Free SSL/TLS certificates
• Scott Helme — Security Headers scanner
• Google PageSpeed Insights — Measure page performance