Technical SEO Audit Checklist: 15 Critical Issues to Fix in 2025

Your website might look great to visitors, but is Google seeing it the same way? Technical SEO issues can silently sabotage your rankings, causing your pages to be ignored, misunderstood, or penalised by search engines. In this comprehensive guide, we'll walk through the 15 most critical technical SEO issues we find in our audits and show you exactly how to fix them.

What is a Technical SEO Audit?

A technical SEO audit is a comprehensive analysis of your website's technical health from a search engine's perspective. Unlike content or off-page SEO, technical SEO focuses on the infrastructure that allows search engines to crawl, index, and rank your pages effectively.

Think of it like a health check-up for your website. Just as a doctor examines your vital signs, a technical SEO audit examines your site's vital metrics: page speed, mobile-friendliness, crawlability, and indexation status. Without addressing these fundamentals, even the best content won't reach its ranking potential.

Crawlability Issues

Crawlability refers to search engines' ability to access and navigate your website. If Googlebot can't crawl your pages, they simply won't appear in search results—no matter how good your content is. Here are the most common crawlability issues we encounter:

1. Robots.txt Blocking Important Pages

Your robots.txt file tells search engines which pages they can and cannot crawl. A misconfigured robots.txt can accidentally block your most important pages from being indexed. Common mistakes include blocking CSS and JavaScript files (which Google needs to render pages), blocking entire directories that contain important content, or using overly broad disallow rules that catch pages you want indexed.

2. Broken Internal Links

Internal links help search engines discover and understand the relationship between your pages. Broken internal links (404 errors) waste crawl budget and create poor user experiences. Every broken link is a dead end for both users and search engines. Use tools like Screaming Frog to crawl your site and identify these issues systematically.

3. Slow Server Response Time

If your server takes too long to respond, Googlebot may give up before crawling all your pages. This is particularly problematic for large sites. Aim for a Time to First Byte (TTFB) under 200ms. Common fixes include upgrading hosting, implementing server-side caching, optimising database queries, and using a content delivery network (CDN).

Indexation Problems

Once Google can crawl your pages, the next challenge is ensuring they get indexed. Indexation issues can prevent perfectly good content from appearing in search results, even when there are no crawling problems.

4. Duplicate Content

Duplicate content confuses search engines about which version of a page to rank. This commonly occurs with www vs non-www versions, HTTP vs HTTPS, trailing slashes, URL parameters, and pagination. Implement canonical tags to specify your preferred version and set up proper redirects to consolidate duplicate URLs.

5. Missing or Incorrect Canonical Tags

Canonical tags tell Google which URL represents the master copy of a page. Missing canonicals leave Google guessing, while incorrect canonicals can point to the wrong page entirely—or worse, to a non-existent page. Always audit your canonical implementation to ensure every page has a self-referencing canonical or points to the correct master version.

6. Noindex Tags on Important Pages

A noindex meta tag tells Google not to include a page in search results. Sometimes these tags are accidentally left on important pages after development or staging environments are merged to production. Check Google Search Console's Coverage report regularly to identify pages excluded by noindex that shouldn't be.

Core Web Vitals

Core Web Vitals are Google's metrics for measuring user experience. They became a confirmed ranking factor in 2021 and have only grown in importance since. Poor Core Web Vitals can hurt your rankings, especially in competitive niches where other ranking factors are equal.

7. Largest Contentful Paint (LCP)

LCP measures how long it takes for the largest content element (usually a hero image or heading) to load. Google considers anything under 2.5 seconds as "good." Improve LCP by optimising and compressing images, implementing lazy loading for below-the-fold content, using modern image formats like WebP, and leveraging a CDN for faster delivery.

8. Cumulative Layout Shift (CLS)

CLS measures visual stability—how much the page layout shifts unexpectedly while loading. A score above 0.1 indicates problems that frustrate users. Fix CLS by always specifying image and video dimensions, reserving space for ad slots and embeds, and avoiding dynamically injected content above existing content.

9. Interaction to Next Paint (INP)

INP replaced First Input Delay (FID) in March 2024 and measures overall page responsiveness throughout the user's visit. Aim for under 200ms. Improve INP by optimising JavaScript execution, breaking up long tasks into smaller chunks, reducing main thread blocking, and deferring non-critical scripts.

Site Architecture

Your site's architecture affects how search engines understand content hierarchy and distribute PageRank throughout your site. A well-structured site helps search engines find and prioritise your most important pages.

10. Deep Page Depth

Important pages should be reachable within 3 clicks from the homepage. Pages buried 5+ clicks deep receive significantly less crawl attention and link equity. Flatten your architecture by adding internal links from high-authority pages, improving navigation, and creating hub pages that link to related content.

11. Orphan Pages

Orphan pages have no internal links pointing to them. Without internal links, these pages are difficult for search engines to discover and may never get indexed. Compare your sitemap URLs against pages found during a crawl to identify orphans, then add appropriate internal links or remove pages that are no longer needed.

Technical SEO Priority Matrix

Not all technical SEO issues are created equal. Here's how to prioritise your fixes based on impact and implementation difficulty:

Critical Priority (Fix Immediately): Robots.txt blocking important pages, noindex on key pages, server errors (5xx), and broken redirects. These issues completely prevent indexing and should be addressed within 24-48 hours of discovery.

High Priority (Fix Within 1 Week): Core Web Vitals failures, duplicate content issues, missing canonical tags, and slow page speed. These significantly impact rankings and user experience.

Medium Priority (Fix Within 1 Month): Broken internal links, deep page architecture, missing meta descriptions, and image optimisation. These affect user experience and crawl efficiency but won't cause immediate ranking drops.

Low Priority (Ongoing Maintenance): Orphan pages, redirect chains, minor CLS issues, and schema markup improvements. Address these during regular maintenance cycles.

Next Steps: Taking Action

Now that you understand the critical technical SEO issues to look for, it's time to take action. Start by running a comprehensive crawl of your site with Screaming Frog or a similar tool. Then check Google Search Console for any coverage issues, Core Web Vitals problems, or manual actions.

Create a prioritised list of issues based on the framework above, and tackle critical issues first. Document everything you change so you can measure the impact on rankings and traffic over the following weeks.

Remember, technical SEO isn't a one-time task—it's an ongoing process. Schedule regular audits to catch issues before they impact your rankings. Set up alerts in Google Search Console for coverage issues and Core Web Vitals regressions. The sites that win in search are those that maintain technical excellence consistently over time.