Technical SEO is the least visible part of search engine optimisation, and at the same time the part where we find the most errors during a baseline review. A site can look beautiful and still have pages Google never reaches. This technical SEO checklist helps you track down that kind of error yourself.
What exactly is technical SEO?
Technical SEO covers all changes to the technology of your website that help search engines find your pages (crawl), store them (index) and understand them. So it is not about the text on your pages, nor about links from other sites, but about the foundation underneath. Without that foundation, the finest content makes little difference.
The technical SEO checklist in 11 points
Work through the points in this order. The first four determine whether Google can see your pages at all, the rest determine how well that goes.
| # | Item | Main tool |
|---|---|---|
| 1 | Indexing | Google Search Console |
| 2 | Robots.txt | Browser, Search Console |
| 3 | XML sitemap | Search Console |
| 4 | Canonicals | Crawler (for example Screaming Frog) |
| 5 | Status codes and redirects | Crawler, Search Console |
| 6 | Speed and Core Web Vitals | PageSpeed Insights |
| 7 | Mobile | Your own phone, PageSpeed Insights |
| 8 | Internal links | Crawler |
| 9 | Structured data | Rich Results Test |
| 10 | Duplicate content | Crawler, site: search |
| 11 | HTTPS | Browser, Search Console |
1. Indexing: are your pages in Google?
Start in Google Search Console with the Pages report (under Indexing). There you see which URLs are indexed and which are not, with the reason. Pay particular attention to pages you do want to rank but which are “Excluded by noindex tag” or “Crawled, currently not indexed”.
Quick check: type site:yourdomain.nl into Google. If you have 40 pages and Google shows 400, you probably have a problem with filters, tags or parameters.
2. Robots.txt: are you accidentally blocking too much?
The file yourdomain.nl/robots.txt tells crawlers which parts of your site they may not visit. Two classic mistakes:
- A
Disallow: /left over from before a new site went live. That shuts off the whole site. - Blocking CSS or JavaScript folders. Google needs to load those files to render your pages the way a visitor sees them.
Good to know: blocking a page in robots.txt does not remove it from the index. If you want a page out of Google, use a noindex tag on the page itself and let robots.txt allow that page.
3. XML sitemap: an up-to-date list of your important pages
A sitemap is a file with all the URLs you want indexed. Check that:
- the sitemap exists and has been submitted in Search Console;
- it only contains pages that return a 200 status code, are not noindex and have a canonical pointing to themselves;
- the sitemap updates automatically when you add or remove pages.
A sitemap may contain a maximum of 50,000 URLs. Larger sites split the sitemap into several files with a sitemap index.
4. Canonicals: which version counts?
With a canonical tag (<link rel="canonical">) you indicate which URL is the main version when the same content is available at several addresses. Think of a product page with and without a filter parameter, or with and without a trailing slash.
Common mistakes: canonicals pointing to a 404 or a redirect, every page pointing to the homepage (happens with badly configured plugins), or pages without a canonical. Note: a canonical is a strong signal, not a command. Google can deviate if other signals point the other way.
5. Status codes and redirects
Every URL returns a status code. The most important ones:
| Code | Meaning | Action |
|---|---|---|
| 200 | Page works | Nothing |
| 301 | Permanently moved | Fine, as long as the destination is right |
| 302 | Temporarily moved | Replace with 301 if it is permanent |
| 404 | Not found | Redirect if there is a good alternative, otherwise leave |
| 500 | Server error | Fix immediately |
Crawl your site and look for redirect chains (A to B to C) and redirect loops. Every extra step costs crawl budget and slows the visitor down. Also check that old URLs have been redirected properly after a migration. Forgetting this is one of the most expensive technical SEO mistakes we come across: you lose in one go rankings you built up over years.
6. Speed and Core Web Vitals
Google measures the user experience with three Core Web Vitals:
- LCP (Largest Contentful Paint): how quickly the largest element appears on screen. Guideline: within 2.5 seconds.
- INP (Interaction to Next Paint): how quickly the page responds to a click or tap. Guideline: within 200 milliseconds.
- CLS (Cumulative Layout Shift): how much the page jumps around while loading. Guideline: below 0.1.
You find these figures in PageSpeed Insights and in Search Console. Look above all at the field data (the experience of real visitors), not just the lab score. The biggest gain is usually in oversized images, too many external scripts and slow hosting.
7. Mobile
Google indexes the mobile version of your site. Whatever is on desktop but left out on mobile does not count. Check on your phone that all content, internal links and structured data are also present on mobile and that buttons and text are usable without zooming.
8. Internal links
Internal links tell Google which pages are important and help crawlers find everything. Use a crawler to look for:
- orphan pages: pages without a single internal link pointing to them;
- pages that can only be reached via five or more clicks from the homepage;
- internal links to redirects or 404s.
Your most important pages should be reachable within three clicks from the homepage.
9. Structured data
With structured data (according to schema.org, usually as JSON-LD) you explain what is on a page: a product with price and stock, a business with address and opening hours, an FAQ. This can produce rich results in Google, such as stars or prices in the search results.
Check your pages with Google’s Rich Results Test. Common errors: invalid JSON, empty fields and markup that does not match what is visible on the page.
10. Duplicate content
Duplicate content arises more often by accident than by design. Think of http and https or with and without www both being reachable, product variants with almost identical text, filter parameters and a staging environment that has been indexed. Solutions: redirects for domain variants, canonicals for parameters and variants, and a password on staging environments.
11. HTTPS
Your whole site should run over https, with a valid certificate and a redirect from all http variants. Also check for mixed content: pages that load over https but still fetch images or scripts over http. Browsers then show warnings and that costs trust.
Technical SEO errors we see most often
In our technical SEO audits the same patterns keep coming back:
- Old URLs without a redirect after a new website or migration.
- Noindex or a robots block that went live by accident.
- Filter pages generating thousands of empty or duplicate URLs.
- Images of several megabytes on the homepage.
- Structured data that is there, but invalid or with empty fields.
- Tracking that is wrong, so you cannot prove your improvements.
That last one does not officially fall under technical SEO, but it is the first check we do. Read more about it in GA4 and consent mode.
From our own experience: at our own companies Djunes and Rij Ruimer we always started with the technology before writing content. At Djunes organic traffic grew by 187 percent in twelve months. Part of that growth came from content, but the technology had to be right first for that content to rank.
How do you approach a technical SEO audit?
You do a technical SEO analysis in three steps:
- Collect. Crawl your site, export the reports from Search Console and run PageSpeed Insights on your most important page types.
- Prioritise. A noindex on your most important category page is urgent, a missing alt text on an icon is not. Sort by impact and by how many pages it affects.
- Fix and verify. Implement the fixes, request a new crawl in Search Console and check after a few weeks that the errors are gone.
Technical SEO is never finished. Every new plugin, every theme and every content change can break something. So schedule a fixed check, for example every quarter.
What comes after the technology?
Once the foundation is in place, the rest follows: keyword research, SEO copywriting and building links. With SEO, count on four to six weeks on average before you see the first results.
At Stijgt every SEO programme starts with a baseline review in which this checklist is a fixed part, alongside an analysis of your tracking and your marketing channels. Want to know how your site is doing? Get in touch or see our SEO service.