Technical SEO: the checklist that decides whether Google finds you

Technical SEO is the work of making a website possible for search engines to find, read, understand and trust. It isn't about what the page says, but about everything around it: how fast it loads, whether the robots are let in, how the URLs are built and what happens on mobile.

It is the least glamorous part of SEO and the one that pays off fastest when something is broken. A page with excellent content that Google can't read doesn't rank at all, and that is surprisingly common.

Start here: can Google find and read the page?#

Before anything else, check the four things that can make the entire site invisible.

robots.txt doesn't block what it shouldn't

The file sits at yourdomain.com/robots.txt and tells robots what they may visit. The line Disallow: / blocks the whole site. It sounds unlikely, but that line is routinely set during development, and it is left in place at launch more often than anyone wants to admit.

Pages aren't set to noindex

A page with <meta name="robots" content="noindex"> is removed from Google even if everything else is perfect. Same story here: standard in a test environment, a disaster in production.

The site is indexed

Search for site:yourdomain.com on Google. Do you see your pages? Is the number roughly what you expect? Too few means indexing problems. Significantly more means that pages which shouldn't be in the index have ended up there.

Sitemap and Search Console are in place

An XML sitemap at yourdomain.com/sitemap.xml tells Google which pages exist. Submit it in Google Search Console, which is also the only place where you can see which indexing problems Google has actually found.

Page speed and Core Web Vitals#

Google measures three things about the user experience, and they affect both rankings and how many people stay.

• LCP (Largest Contentful Paint): when the largest content on the page appears. Should be under 2.5 seconds.
• INP (Interaction to Next Paint): how quickly the page responds when someone clicks. Should be under 200 milliseconds.
• CLS (Cumulative Layout Shift): how much the content jumps around while loading. Should be under 0.1.

What most often ruins them, in descending order:

1. Uncompressed images. A 4 MB background image is the most common single cause. Use WebP or AVIF, and scale images to the size they are actually displayed at.
2. Video that loads automatically. A hero video on the home page can cost several megabytes on its own before anything appears.
3. Too much JavaScript. Every plugin, chat widget and tracking script has a cost.
4. Images without set dimensions. Without a width and height, the browser doesn't know how much space to reserve, and the content jumps.
5. Fonts that load late. Use font-display: swap so the text shows immediately.

Measure in Google's PageSpeed Insights. Look above all at the field data, meaning measurements from real visitors. The lab data is a simulation and can look considerably better than reality.

Mobile-friendliness#

Google indexes the mobile version of the page. What isn't visible on mobile, in practice, doesn't count.

Check that the text is readable without zooming, that buttons and links can be hit with a thumb, that nothing sticks out sideways and that the same content exists on mobile as on desktop. The last one is easy to miss when collapsible sections are used heavily.

Want to be more visible on Google? Read about SEO →

URL structure and internal links#

URLs should make sense. /services/web-development says something. /index.php?id=42 does not.

One page, one address. The page must not exist both with and without www, on both http and https, and both with and without a trailing slash. Choose one variant and point the others to it with permanent redirects.

Set a canonical. The <link rel="canonical"> tag tells Google which address is the real one when the same content can be reached in several ways.

Link internally. Every important page should be reachable within three clicks of the home page. Internal links show Google what belongs together and what matters, and they are the cheapest SEO tool there is, because you control them entirely yourself.

Structured data#

Structured data (Schema.org, usually in the JSON-LD format) explains to search engines what the content means: that this is a business, that that is an article with an author and a date, that this is a frequently asked question.

Relevant types for most businesses:

• Organization or LocalBusiness: company details, address, opening hours
• BreadcrumbList: the page's place in the structure
• Article or BlogPosting: for blog posts
• FAQPage: for frequently asked questions
• Product and Review: for e-commerce

The effect is twofold: it can give a richer display in the search results, and it makes the content easier for AI-driven search answers to cite correctly. Always validate with Google's Rich Results Test, since incorrect structured data is worse than none at all.

Security#

HTTPS is a minimum requirement, not an improvement. Without a valid certificate, browsers warn the visitor, and it doesn't matter how well the page ranks if people back out at the warning.

Also check that the certificate actually renews automatically. An expired certificate can knock a site out completely over a weekend.

Common faults we find in reviews#

• The site blocked in robots.txt after launch
• The same page title on every page, or the title "Home"
• Images of several megabytes without compression
• No sitemap, or a sitemap listing pages that return 404
• Heading levels that skip, from H1 straight to H4
• Content that only exists after JavaScript has run, with no fallback
• Old URLs that return 404 instead of being redirected
• Several H1 headings on the same page

How to prioritise#

If you only have time for three things: make sure the site is indexable, compress the images and give every page a unique title. That is where the effect per hour spent is greatest.

Technical SEO also goes stale, in the sense that it breaks on its own: a new plugin, a repointed domain or a missed redirect can wipe out work that has functioned for years. Check after every major change to the site.

If you want to know what is actually slowing your site down, get in touch and we will go through it. Also read about what SEO is for the bigger picture, or about how we work with web development.