Your website could be well-designed, packed with useful content, and priced competitively. But if the technical foundations aren’t right, Google may struggle to find it, crawl it, or rank it where it deserves to be. Technical SEO is the part of search optimisation that most business owners never see but that affects everything they care about: traffic, rankings, and enquiries.
This technical SEO checklist walks you through the key areas to audit, with a plain-English explanation of what each check involves and why it matters. Whether you’re reviewing your own site or briefing an agency, this is where to start.
What Is Technical SEO (And Why Does It Matter)?
Technical SEO refers to the behind-the-scenes work that helps search engines find, crawl, index, and rank your website correctly. It’s different from on-page SEO (your content and keywords) and off-page SEO (backlinks and authority). Think of it as the infrastructure your entire SEO strategy is built on.
A site with strong content but poor technical foundations is like a well-stocked shop with no signage and a broken front door. The goods are there, but customers can’t get in. Google sends automated bots (called crawlers) to visit and understand your site. Technical SEO ensures those bots can access every page, understand its purpose, and pass that understanding back to Google’s index.
When technical issues are present, they often suppress rankings across the entire site, not just individual pages. That’s why fixing technical problems typically delivers faster, broader results than creating new content alone.
The Technical SEO Checklist: 10 Areas to Audit
Work through each area in order. The first few sections tend to have the highest impact, particularly for sites that haven’t had a technical review before.
1. Crawlability and Indexation
Google can only rank what it can find and read. Crawlability issues prevent Google’s bots from accessing your pages in the first place. Indexation issues mean pages are found but not added to Google’s index, so they can’t appear in search results.
Start by checking your robots.txt file. This file tells search engine crawlers which pages they’re allowed to visit. A misconfigured robots.txt can accidentally block your entire site from being crawled. You can view it by adding /robots.txt to your domain (e.g. yourdomain.co.uk/robots.txt).
Next, review your XML sitemap. This is a file that lists all the important pages on your site, giving Google a clear map to follow. It should be submitted in Google Search Console and updated automatically whenever you add or remove pages. Check that it contains the right pages and doesn’t include URLs you’d rather not have indexed (old drafts, thin pages, parameter URLs).
Use Google Search Console to identify any pages Google is struggling to index. The Coverage or Pages report shows which URLs are indexed, which are excluded, and which have errors. Any pages marked with warnings or errors are worth investigating.
What to check:
- Is your robots.txt accessible and correctly configured?
- Is your XML sitemap submitted and free of errors in Search Console?
- Are your most important pages indexed?
- Are there any pages being blocked that shouldn’t be?
2. Site Speed and Core Web Vitals
Page speed has been a Google ranking factor for over a decade. Core Web Vitals, introduced as a ranking signal in 2021, take this further by measuring the real-world user experience of your pages across three dimensions: loading speed (LCP), visual stability (CLS), and interactivity (INP).
Largest Contentful Paint (LCP) measures how quickly the largest visible element on the page loads. Google recommends under 2.5 seconds. A slow LCP is often caused by large uncompressed images, slow server response times, or render-blocking resources like unminified CSS and JavaScript.
Cumulative Layout Shift (CLS) measures how much the page jumps around as it loads. Unexpected layout shifts frustrate users and are often caused by images without defined dimensions or ads loading after the page content. Google recommends a CLS score below 0.1.
Interaction to Next Paint (INP) measures how quickly the page responds to user interactions. A sluggish INP score usually points to heavy JavaScript that’s blocking the main thread.
You can test your Core Web Vitals scores in Google Search Console (under the Experience section) or through Google PageSpeed Insights, which also gives page-level recommendations for improvement.
For WordPress sites specifically, common culprits for poor speed scores include page builder bloat, unminified plugin assets, and images that haven’t been compressed before upload. A well-built WordPress site, one that’s been developed with performance in mind from the start rather than optimised retrospectively, should consistently score above 90 in PageSpeed Insights. Our WordPress development service addresses performance as part of the build, not as an afterthought.
What to check:
- LCP under 2.5 seconds on both mobile and desktop
- CLS score below 0.1
- INP under 200 milliseconds
- PageSpeed Insights score above 90 (mobile and desktop)
- Unminified JS/CSS flagged and addressed
- Images compressed and correctly sized
3. Mobile-First Indexing
Google now uses the mobile version of your site as the primary version for indexing and ranking. If your mobile experience is poor, your rankings suffer regardless of how good the desktop version looks.
Mobile-first indexing doesn’t just mean your site scales to fit smaller screens. It means the mobile version must contain the same content, structured data, and internal links as the desktop version. Sites that hide content on mobile (common with some tab and accordion implementations) may find that hidden content is not indexed.
Use Google Search Console’s URL Inspection tool to check how Googlebot sees any given page. You can also use Chrome DevTools to emulate mobile devices and spot any content or functionality that’s missing or broken on smaller screens.
What to check:
- Does the mobile version contain all the same key content as desktop?
- Are all internal links accessible on mobile?
- Is tap target spacing adequate (buttons and links easy to tap)?
- Does the site pass Google’s mobile usability test in Search Console?
4. HTTPS and Site Security
HTTPS has been a Google ranking signal since 2014 and is now standard expectation rather than a differentiator. If your site is still running on HTTP, it’ll be flagged as “Not Secure” in Chrome, which erodes trust and likely suppresses rankings.
Check that your SSL certificate is valid and not close to expiry. Most hosting providers renew these automatically, but it’s worth confirming. You should also verify that all pages on your site load via HTTPS and that the HTTP version of any URL redirects correctly to HTTPS (not the other way around).
Mixed content is a related issue: pages that load via HTTPS but include resources (images, scripts, stylesheets) still served over HTTP. Mixed content warnings can appear in the browser and may prevent the page from displaying correctly.
What to check:
- Is your SSL certificate valid and not expiring soon?
- Does HTTP redirect correctly to HTTPS across all pages?
- Are there any mixed content warnings in the browser console?
- Is your domain secured with HSTS?
5. URL Structure and Site Architecture
A clean URL structure helps both users and search engines understand how your site is organised. Clear, descriptive URLs are easier to read, share, and rank for relevant terms. Messy or inconsistent URLs create confusion and dilute link equity.
Good URL structure follows a logical hierarchy that reflects your content architecture. For example, /services/web-design/ is cleaner than /page?id=42&cat=3. Keep URLs short, lowercase, and separated by hyphens rather than underscores.
Consistency matters too. If your CMS uses trailing slashes by default (as WordPress does), all internal links should include the trailing slash. Links that point to a URL without the trailing slash will trigger a redirect, and redirect chains dilute the equity passing to your target pages.
Site architecture refers to how your pages connect to one another. Pages should be reachable within three clicks from the homepage where possible. Orphaned pages (those with no internal links pointing to them) receive no equity from the rest of the site and are often harder for Google to discover and index.
What to check:
- Are URLs descriptive, lowercase, and hyphen-separated?
- Is trailing slash usage consistent across all internal links?
- Are your most important pages within three clicks of the homepage?
- Are there any orphaned pages with no internal links?
- Are parameter-based URLs being handled correctly (excluded from index or canonicalised)?
6. Canonical Tags and Duplicate Content
Canonical tags tell Google which version of a page is the “original” when multiple URLs contain the same or very similar content. Without them, Google has to guess, and it sometimes picks the wrong one.
Duplicate content can arise in several ways: HTTP vs HTTPS versions of a page both being accessible, www vs non-www versions, trailing slash vs non-trailing slash variants, or URL parameters creating multiple versions of the same page (common in ecommerce filtering). Each of these can dilute your ranking signals because Google splits its attention between multiple versions rather than consolidating it on one.
The canonical tag (<link rel=”canonical”> in the HTML head) should be present on every page, even if it’s self-referencing. This is particularly important for WordPress sites where plugins or theme code can sometimes generate duplicate or near-duplicate pages.
What to check:
- Does every page have a canonical tag pointing to the correct URL?
- Are HTTP and HTTPS versions unified?
- Are www and non-www versions unified with a redirect?
- Are URL parameter pages handled correctly?
- Are there any unintentional near-duplicate pages?
7. Redirect Management
Redirects pass link equity (and users) from one URL to another. Used correctly, they’re an essential part of site maintenance. Used poorly, they create problems that build up silently over time.
A 301 redirect is a permanent redirect. It signals to Google that a page has moved for good, passing most of its equity to the new URL. These are what you should use when you change a URL, delete a page, or restructure your site. A 302 redirect is temporary and does not pass equity in the same way, so using 302s when you mean 301 is a common and costly mistake.
Redirect chains are where one redirect points to another, which points to another. Each hop in a chain bleeds equity. If your site has accumulated redirect chains over time (common after redesigns or URL changes), cleaning them up is worth the effort. All redirects should point directly to the final destination URL in a single hop.
Broken links (those pointing to pages that return a 404 error) are both a crawlability issue and a user experience issue. They waste crawl budget and create dead ends for visitors. Google Search Console flags crawl errors, and tools like Screaming Frog can surface broken internal links quickly.
What to check:
- Are all redirects 301 (permanent) rather than 302 (temporary)?
- Are there any redirect chains (more than one hop)?
- Are there any broken internal links returning 404 errors?
- When pages were removed or restructured, were redirects set up?
8. Internal Linking
Internal links connect your pages to one another and serve two purposes: they help users navigate, and they help Google understand the relative importance of each page on your site. Pages with more internal links pointing to them receive more equity and signal greater importance to search engines.
For hub-and-cluster content architectures (where a pillar page covers a broad topic and links to more detailed cluster pages), internal linking is the structural backbone. The hub page passes equity to the clusters beneath it, and the clusters link back, reinforcing topical authority across the whole group.
Anchor text (the clickable words in a link) also carries a relevance signal. Descriptive anchor text like “our web design process” is more informative to Google than generic text like “click here” or “read more”. Use descriptive anchor text throughout and avoid over-optimising by repeating the same anchor text for the same page too many times.
If you want to understand more about how SEO strategy works at a content level, our guide to what’s included in a website audit covers how we assess a site’s content and linking structure as part of a full review.
What to check:
- Do your most important pages have multiple internal links pointing to them?
- Are there orphaned pages with zero or one internal links?
- Is anchor text descriptive and varied?
- Do cluster pages link back up to their parent hub pages?
- Are internal links consistent (trailing slash, canonical URL)?
9. Structured Data and Schema Markup
Structured data (schema markup) is code added to your pages that tells search engines exactly what each piece of content represents. It doesn’t directly affect rankings but it can significantly improve how your results appear in Google, which affects click-through rates.
Common schema types for business websites include:
- LocalBusiness: tells Google your business name, address, phone number, opening hours, and service area
- FAQPage: marks up question-and-answer sections, making them eligible to appear as expandable results in search
- Service: describes a specific service you offer, including its name, description, and geographic coverage
- BreadcrumbList: marks up your navigation trail, which can appear in search results
- Article: for blog posts and news articles
You can validate your schema markup using Google’s Rich Results Test. This shows you what rich results your pages are eligible for and flags any errors in the markup.
Schema is increasingly important in the context of AI-powered search results and generative engine optimisation (GEO). When AI assistants draw on web content to answer questions, well-structured data helps your site’s information get interpreted accurately. If you haven’t looked at how your site appears in AI-generated answers, our GEO service covers this in detail.
What to check:
- Is LocalBusiness schema in place on your homepage and key local pages?
- Are FAQPage schemas implemented on pages with Q&A sections?
- Is BreadcrumbList schema applied across the site?
- Are there any schema errors flagged in Google Search Console?
- Do the Rich Results Test results match what you’d expect?
10. Image Optimisation
Images are often the biggest contributor to slow page load times. They’re also an opportunity for additional search visibility through Google Image Search and a source of accessibility improvements that benefit all users.
Every image on your site should have a descriptive alt text attribute. Alt text serves two purposes: it tells screen readers what the image shows (important for accessibility), and it gives Google additional context about the image and the page it appears on. Alt text should describe the image accurately and naturally. For most images on a business website, a short phrase like “Yellow Circle team working on a client SEO strategy” is appropriate. Avoid stuffing keywords into alt text: write it as you’d describe the image to someone who can’t see it.
Image file sizes should be kept as small as possible without visible quality loss. Use modern formats like WebP where browser support allows. Serve images at the correct display size (don’t serve a 2,000px wide image in a 400px column). Lazy loading (loading images only when they scroll into view) can also improve initial page load times significantly.
What to check:
- Do all images have descriptive, accurate alt text?
- Are image file sizes compressed without visible quality loss?
- Are images served in modern formats (WebP where possible)?
- Are images sized to their display dimensions?
- Is lazy loading implemented for images below the fold?
How Often Should You Run a Technical SEO Audit?
A full technical audit should happen at least once a year, or any time you make significant changes to your site: a redesign, a CMS migration, a URL restructure, or a major plugin or theme update. Even without major changes, sites accumulate technical debt over time. Pages get deleted without redirects, plugins add unminified assets, and crawl errors creep in.
Outside of full audits, Google Search Console is worth checking monthly. It surfaces crawl errors, coverage issues, Core Web Vitals problems, and manual actions (the rare but serious cases where Google has penalised a site for policy violations). It’s a free tool and the closest thing you can get to Google’s actual view of your site.
For businesses investing in SEO through a digital marketing agency, technical audits should be part of the ongoing relationship, not a one-off exercise. Rankings depend on the whole system working correctly, and that system needs regular maintenance. Our website maintenance service keeps your site’s technical health in good shape between audits, covering security updates, performance monitoring, and WordPress core and plugin management.
Technical SEO vs On-Page SEO: What’s the Difference?
This is one of the most common questions we hear when talking to business owners who’ve been told they need “SEO work” done. The two are related but distinct.
Technical SEO covers the infrastructure: crawlability, indexation, speed, security, site architecture, and structured data. It’s about ensuring that search engines can access, understand, and evaluate your site correctly. This work is largely invisible to human visitors but has a significant impact on rankings.
On-page SEO covers the content layer: keyword targeting, heading structure, meta titles and descriptions, content depth, and internal link anchor text. This work is visible to users and directly shapes how a page ranks for specific search terms.
Both matter, and neither works particularly well in isolation. Strong content on a technically broken site won’t rank. A technically flawless site with thin content won’t rank either. The checklist above addresses the technical side; if you need support with both, our SEO service covers the full picture, from technical foundations through to content strategy and authority building.
What Does a Professional Technical SEO Audit Include?
A basic self-audit using the checklist above is a useful starting point. A professional technical SEO audit goes further, using specialist tools to surface issues that aren’t visible through manual inspection, and providing prioritised recommendations based on the likely impact of each fix.
At Yellow Circle, a technical audit is typically the first step before any ongoing SEO engagement. We use Google Search Console, a full site crawl, and performance analysis to build a clear picture of where your site stands and what needs to happen first. Some issues need a developer to resolve (unminified assets, redirect chains, missing schema); others can be addressed in your CMS directly.
If you’re unsure whether your site has technical issues holding back its performance, a website audit is the clearest way to find out. We review technical health alongside content quality and authority signals, so you get a complete picture rather than a list of isolated fixes.
Ready to Get the Technical Foundations Right?
Technical SEO isn’t the most visible part of growing a website’s performance, but it’s often the most foundational. Get it wrong and everything else you invest in content and links is working against the grain. Get it right and the rest of your SEO activity has a solid base to build on.
If you’d like a clear, honest assessment of where your site stands technically, get in touch and we’ll take a look. No jargon, no obligation, just a straightforward conversation about what’s holding your site back and what to do about it.
