Technical SEO Checklist: 40+ Issues That Kill Your Rankings
Key Takeaways
- Technical SEO is the foundation of all search visibility - without it, even world-class content and backlinks won't rank.
- The most common ranking killers are crawl blocks, slow page speed, duplicate content, and broken internal links.
- Core Web Vitals (LCP, INP, CLS) are now confirmed ranking signals - failing scores directly suppress rankings.
- Run a comprehensive audit quarterly, with automated monitoring catching critical issues between audits.
- Technical SEO has the highest ROI of any SEO activity - fixes are one-time but benefits compound forever.
Table of Contents
Technical SEO is the invisible engine behind every successful ranking. You can create the best content in the world and build hundreds of premium backlinks, but if Google can't properly crawl, index, and render your pages - none of it matters.
This checklist covers 40+ technical issues organised by category, with severity ratings and fix guidance. Whether you're auditing your own site or evaluating a client's, work through each section systematically.
Crawlability & Indexation Checklist
| Check | Severity | What to Look For |
|---|---|---|
| Robots.txt not blocking important pages | Critical | Ensure robots.txt doesn't disallow key directories. Test at /robots.txt |
| XML sitemap exists and is submitted | Critical | Sitemap lists all indexable URLs, no 404s, submitted to Google Search Console |
| No noindex on important pages | Critical | Check meta robots tags - accidental noindex kills pages from search entirely |
| Canonical tags are correct | High | Each page should self-reference or point to the correct canonical version |
| No orphan pages | High | Every important page should be reachable through internal links |
| Crawl budget not wasted | Medium | Block faceted navigation, parameter pages, and internal search from crawling |
| Index coverage errors resolved | High | Check GSC Index Coverage report for excluded/error pages |
| Pagination handled correctly | Medium | Use self-referencing canonicals on paginated series (rel=prev/next deprecated) |
Site Speed & Core Web Vitals
Google's Core Web Vitals are confirmed ranking signals. Pages failing CWV are actively suppressed in rankings.
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | ≤ 2.5s | 2.5-4.0s | > 4.0s |
| INP (Interaction to Next Paint) | ≤ 200ms | 200-500ms | > 500ms |
| CLS (Cumulative Layout Shift) | ≤ 0.1 | 0.1-0.25 | > 0.25 |
Speed Optimisation Checklist
- Image optimisation: Use WebP/AVIF format, proper sizing, lazy loading for below-fold images
- Minimise render-blocking resources: Defer non-critical CSS/JS, inline critical CSS
- Enable compression: Gzip or Brotli compression for all text-based resources
- Browser caching: Set appropriate cache-control headers for static assets
- CDN: Serve assets from geographically distributed edge servers
- Minimise third-party scripts: Each tracking pixel, chat widget, and ad script adds load time
- Preload critical resources: Use <link rel="preload"> for fonts, hero images, and critical CSS
- Reduce server response time: Target TTFB (Time to First Byte) under 200ms
Mobile Optimisation
Google uses mobile-first indexing, so your mobile version is the primary version Google evaluates. Ensure:
- Responsive design works across all device sizes (test at 320px, 375px, 414px, 768px widths)
- No content hidden on mobile that's visible on desktop (Google may not index hidden content)
- Touch targets are at least 48x48px with adequate spacing
- No horizontal scrolling required
- Text readable without zooming (16px minimum font size)
- No intrusive interstitials or popups that cover content on mobile
URL Structure & Architecture
- Clean URLs: Use descriptive, keyword-relevant URLs (example.com/seo-guide/ not example.com/?p=123)
- Logical hierarchy: URL structure reflects site architecture (domain/category/page)
- Consistent trailing slashes: Choose one format and redirect the other
- No duplicate URLs: www vs non-www, HTTP vs HTTPS, trailing slash variations all redirected to one canonical
- Redirect chains resolved: No more than 1 redirect hop (A→B, not A→B→C→D)
- Internal links use correct URLs: No internal links pointing to redirected URLs
- Flat architecture: Important pages within 3 clicks from homepage
Structured Data & Schema Markup
Structured data helps search engines understand your content and can earn rich snippets in search results:
- Organisation schema on homepage
- BreadcrumbList schema on all interior pages
- Article schema on blog posts (with dated datePublished, current dateModified, author, publisher)
- Product schema on product pages (price, availability, reviews)
- FAQ schema on FAQ sections (earns expandable rich results)
- LocalBusiness schema for local SEO
- HowTo schema for tutorial/guide content
- Validate all schema with Google's Rich Results Test
Security & HTTPS
- Entire site served over HTTPS with valid SSL certificate
- No mixed content warnings (HTTP resources loaded on HTTPS pages)
- HTTP→HTTPS redirects in place for all pages
- HSTS header enabled for security and performance
- CMS, plugins, themes updated to latest versions
- Security headers configured (CSP, X-Frame-Options, X-Content-Type-Options)
Critical: If Google detects malware, phishing, or security issues on your site, it will display a "Deceptive Site Ahead" warning that destroys click-through rates and rankings. Monitor Google Search Console's Security Issues report weekly.
Content & Duplicate Issues
- No thin content: Pages with minimal unique content should be expanded, consolidated, or noindexed
- No duplicate content: Each page should have unique, substantial content
- Canonical tags resolve duplicates: Product variations, filtered pages, and parameter URLs should canonical to the master version
- Unique title tags: Every indexable page needs a unique, descriptive title under 60 characters
- Unique meta descriptions: Compelling descriptions under 155 characters that include target keywords
- Heading hierarchy: One H1 per page, logical H2/H3 nesting
- Image alt text: Descriptive alt text on all images (accessibility + image search)
International & Multilingual SEO
For sites targeting multiple languages or regions:
- Correct hreflang implementation with self-referencing tags
- Hreflang x-default for fallback language
- Consistent hreflang across all language versions (reciprocal references)
- Language-specific sitemaps or hreflang annotations in sitemap
- Avoid auto-redirecting based on IP, let users choose language
Technical SEO Audit Tools
| Tool | Best For | Pricing |
|---|---|---|
| Google Search Console | Index coverage, Core Web Vitals, security issues, manual actions | Free |
| Screaming Frog | Comprehensive site crawling, broken links, redirects, meta data | Free (500 URLs) / £199/yr |
| Ahrefs Site Audit | Automated audits with prioritised issue detection | From $99/mo |
| PageSpeed Insights | Core Web Vitals, lab + field data, optimisation suggestions | Free |
| Schema Validator | Structured data validation and rich result preview | Free |
| Mobile-Friendly Test | Mobile rendering validation | Free |
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Comments
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Really helpful breakdown. Been looking for clear info on this topic.
Great question! This is something we see frequently with our clients. The key is consistency rather than a one-time fix.