Technical SEO guide: inspect the building before you sell it
Nobody buys a house without a building inspection, yet plenty of businesses spend thousands on content for a website nobody has inspected. Technical SEO is that inspection: can Google get in the door, are the rooms it finds the ones you want shown, and is the place pleasant to walk through on a phone?
By the Boltly team · Melbourne
Updated
Inspection summaryWebsite, example grading
Major defectFix this week
- Key pages blocked in robots.txt
- noindex left on after a rebuild
- Pages returning errors instead of 200
- Broken redirects after a migration
Minor defectFix this quarter
- Duplicate URLs with no canonical
- Slow loading on phones
- Pages linked only from the sitemap
- Mobile layouts that drop content
MaintenanceTidy when convenient
- Redirect chains from old moves
- Missing image alt text
Grading is our method. The defects are common examples, not findings from a real site.
What technical SEO covers
Technical SEO is the work that makes sure Google can crawl your pages, index the right versions of them, and show them to people on any device. It covers robots.txt, sitemaps, status codes, canonical tags, internal links, mobile rendering, page speed, HTTPS and structured data. Content and links do the persuading; technical SEO makes sure nothing stops them being seen.
Google publishes the minimum it needs before it will consider showing a page, and it's three requirements long. Everything else here either meets them reliably or makes good pages better.
Googlebot isn't blocked
The page can be reached and isn't disallowed in robots.txt, a firewall or a login screen.
The page works
It returns an HTTP 200 status. Google says client and server error pages aren't indexed.
It has indexable content
The text is in a file type Google supports and the page doesn't break the spam policies.
Meeting all three guarantees nothing: Google says such a page still might not be crawled, indexed or shown. Failing one leaves no chance at all, so a technical audit starts here.
Source: Google Search Central, "Google Search technical requirements", last updated 18 December 2025, read 4 October 2026.
Eight rooms to inspect, and the check for each
Work through them in order: the early rooms decide whether Google sees a page, the later ones how well it performs.
Room 1
The front door: robots.txt
robots.txt tells crawlers which paths to skip. Google stresses it isn't a way to keep a page out of search; a blocked page's URL can still appear. To keep a page out, allow crawling and use noindex.
CheckOpen yoursite.com.au/robots.txt and read every Disallow line. Nothing you sell should be behind one.
Room 2
The floor plan: sitemap and links
Google finds most pages by following links. A sitemap helps larger or newer sites, and WordPress and Shopify generate one anyway.
CheckEvery page you want found should be linked from at least one page a visitor would read, not only listed in the sitemap.
Room 3
The register: indexing
Search Console's Page indexing report lists every URL Google knows about and why any aren't indexed. "Crawled, currently not indexed" means Google fetched the page and chose not to keep it for now; resubmitting won't change that, improving the page might. When dozens of near-identical pages sit in that list (tag archives, one thin page per suburb, supplier product copy), merging them into fewer, fuller pages usually helps more than requesting indexing one by one.
CheckOpen it monthly and look for important pages in the not-indexed list.
Room 4
The duplicates: canonicals
The same content at several URLs (http and https, with and without a trailing slash, shop filters) splits signals. A rel="canonical" tag names the version you prefer. Google calls it a strong signal, but it can still pick a different version if other signals disagree.
CheckURL Inspection shows the canonical you declared and the one Google chose. If they differ, make your menus, in-text links, sitemap and redirects all point at the declared version. Google treats redirects as the strongest signal and sitemap inclusion as a weaker one.
Room 5
The wiring: JavaScript
Google can render JavaScript as long as the files aren't blocked, but sites that build content with JavaScript are harder to get right. Content that loads only after a click or swipe may never be seen.
CheckIn URL Inspection, view the rendered HTML and confirm your main text, links and prices are in it.
Room 6
The small screen: mobile
Google indexes and ranks using the mobile version of a page, crawled as a smartphone. If the mobile layout hides content or headings that desktop shows, the mobile version is what counts.
CheckOpen your top five pages on a real phone. Everything on desktop should be there, if only behind a tab or accordion.
Room 7
The feel: speed and Core Web Vitals
Google's targets are LCP within 2.5 seconds, INP of 200 milliseconds or less and CLS of 0.1 or less, measured at the 75th percentile of real visits. Google says good scores fit what its ranking systems reward, but relevance comes first.
CheckThe Core Web Vitals report in Search Console groups slow pages by type. Fix the template, not each page.
Room 8
The labels: HTTPS and structured data
Serve every page over HTTPS and redirect the http versions. Structured data helps Google understand page details and can make a page eligible for some rich results, as long as it matches what's visible.
CheckRun key pages through the Rich Results Test, and make sure no http page still loads without redirecting.
Sources: Google Search Central, "Introduction to robots.txt", "Learn about sitemaps", "How to specify a canonical URL", "JavaScript SEO basics" (updated 4 March 2026), "Mobile-first indexing best practices", "Understanding Core Web Vitals"; Search Console Help, "Page indexing report". Read 4 October 2026.
Grade every finding before you fix anything
Sort findings into major defects, minor defects and maintenance, as a building inspector would. A crawl tool can produce hundreds of warnings for a twenty-page site, and most don't matter.
Major defect
Stops a page being crawled or indexed, or sends visitors to an error. Accidental noindex tags, blocked folders, broken redirects after a migration, server errors. Fix these first.
Minor defect
Weakens pages that are indexed. Duplicates without canonicals, slow templates, important pages buried four clicks deep, mobile layouts that drop content. Plan a fix within a few months.
Maintenance
Tidy-ups with small or uncertain effect. Old redirect chains, missing alt text on decorative images, a long title tag. Do them when you're in the file anyway.
One example of why grading matters: crawl budget. Many audit tools flag it, but Google's own crawl budget guide is written for large sites, about a million pages changing weekly or ten thousand changing daily, or sites with many URLs stuck as discovered but not indexed. For a typical small business site with a few hundred pages, it's rarely the problem.
After a redesign or platform move, run the major-defect checks again within a day of launch. Most serious technical problems arrive with a rebuild, and our SEO migration checklist covers that step by step.
One more column belongs in the report: who fixes each line. Next to every major and minor defect, write whether it's a setting you can change yourself, a job for your web developer, or a theme or plugin issue, plus a rough time in hours. If you're buying an audit, ask for that column before you pay.
Source: Google Search Central, "Crawl budget management for large sites", last updated 22 July 2026, read 4 October 2026.
A red PageSpeed score isn't a defect report on its own
The big number at the top of PageSpeed Insights comes from a single Lighthouse test run in a simulated environment. It's useful for finding what slows a page, but it doesn't measure what your visitors experienced, and Google's Core Web Vitals assessment isn't based on it.
Owners often meet this score in an unsolicited email: a screenshot of a mobile score in the 30s and an offer to fix it. Before you reply, spend ten minutes on three checks.
- Look for real-user data first. PageSpeed Insights shows field data from real visits (the Chrome User Experience Report) and lab data from the Lighthouse run. If the field panel says your page passes Core Web Vitals, a low lab score is a list of tuning ideas, not an emergency.
- Check the Core Web Vitals report in Search Console. It groups URLs as Good, Needs improvement or Poor from the same real-visit data, showing whether a whole template has a problem. Small sites often show "not enough data", which tells you nobody can quote you a real-user failure either.
- Read the diagnostics, not the dial. If something does need fixing, the useful part is further down: the largest image, the script blocking the page, the layout that jumps. Those become specific jobs with a known owner, usually the theme or a plugin.
Google's PSI documentation says lab data is good for debugging but may miss real-world bottlenecks, while field data captures real experience. So a page can score 45 in the lab and still pass in the field, and the reverse happens.
Source: Google for Developers, "About PageSpeed Insights", last updated 21 October 2024, read 5 October 2026.
Old advice Google has retired
If an audit still asks for any of these, it came from an old template.
The Mobile-Friendly Test
Google removed the tool and the Mobile Usability report from its documentation on 1 December 2023. Use Lighthouse in Chrome, or PageSpeed Insights, and a real phone.
First Input Delay
Interaction to Next Paint (INP) replaced FID as a Core Web Vital in March 2024. Any report still scoring FID is out of date.
How-to rich results
Google stopped showing How-to rich results and removed the documentation.
The cache: operator
Google removed the cache: search operator documentation because it no longer works. Use URL Inspection to see what Google fetched.
FAQ rich results
Google stopped showing FAQ rich results from 7 May 2026 and later removed the documentation. FAQ sections still help readers; they no longer expand in search results.
llms.txt for Google
Google's AI guide now notes that llms.txt files aren't needed for Google Search and won't help or harm rankings.
Blocking the Google-Extended token in robots.txt limits use of your content for some of Google's AI systems outside Search. Google's change log records that it doesn't affect Google Search, so it isn't a technical SEO setting.
Source: Google Search Central, "Documentation updates" change log, entries from September 2023 to June 2026, read 4 October 2026.
Free tools that cover most of the job
For a small site, Google's free tools cover most of the job, and they show what Google actually saw rather than an estimate.
Start in Search Console. Page indexing shows what's in and out of the index and why, URL Inspection shows one page as Googlebot rendered it, Crawl stats shows whether your server struggled, and Core Web Vitals groups slow pages using real visits.
Outside Search Console, PageSpeed Insights and Lighthouse explain why a page is slow, and the Rich Results Test checks structured data. A desktop crawler is worth adding for larger sites, to list every URL, status code and redirect in one sheet.
Our technical SEO service runs this inspection and grades the findings, and the Core Web Vitals guide goes deeper on speed.
Kit listAll free
- Search ConsolePage indexing report
- Search ConsoleURL Inspection tool
- Search ConsoleCrawl stats report
- Search ConsoleCore Web Vitals report
- GooglePageSpeed Insights
- ChromeLighthouse in DevTools
- GoogleRich Results Test
- Your phoneThe real-device check
What to look at first, by type of site
The checklist doesn't change, but the room where the trouble usually is does.
- Brochure sites for trades and services. Usually small, so crawling is rarely the issue. Look at mobile speed, a page per service that's linked from the menu, and leftover noindex tags from the web designer's staging copy.
- Online stores. Filters and sort orders can create thousands of near-identical URLs. Canonicals, sensible internal links to categories and product pages that return 404 or redirect when stock is gone matter most. Our ecommerce SEO page covers this.
- Older sites with years of posts. Duplicate tag and archive pages, orphaned articles and redirect chains from past redesigns build up. A full crawl and a look at the Page indexing report usually turns them up.
- Sites built with JavaScript frameworks. Check the rendered HTML of every template.
Once the building passes inspection, the work moves to the words on each page, which our on-page SEO guide covers, and to local signals if you serve an area, covered in what local SEO is.
Technical SEO, answered
What is technical SEO in simple words?
Technical SEO makes sure Google can reach, read and store your pages, and that they work well on a phone. It covers robots.txt, sitemaps, status codes, canonical tags, internal links, mobile rendering, speed, HTTPS and structured data.
What is the difference between technical SEO and on-page SEO?
On-page SEO is about what a page says: its words, headings and title. Technical SEO is whether Google can reach and index it, and how the site is put together. A great page that's blocked or broken can't rank, so technical problems come first.
What does a technical SEO audit check?
Google's three requirements first, then each of the eight rooms above, from robots.txt to structured data. A good audit grades each finding by how much it matters.
How do I fix "Crawled, currently not indexed"?
Google's help says the page was crawled but not indexed, may be indexed later, and doesn't need resubmitting. Check it isn't a thin or duplicate page, make it more useful than similar pages, and link to it from relevant pages on your site.
Does website speed affect SEO?
It plays a part, but relevance comes first: Google says a slower page that's far more relevant can still outrank a faster one. Speed matters most for keeping visitors who've already arrived.
Do I need an XML sitemap?
Not always. Google says a site of about 500 pages or fewer that's well linked internally may not need one. Larger sites, new sites with few inbound links and media-heavy sites benefit, and most CMSs create one automatically.
My new WordPress site isn't on Google at all. What should I check first?
Open Settings, then Reading, and look at the box labelled "Discourage search engines from indexing this site". Developers often tick it while building and forget it at launch. WordPress's own documentation says that since version 5.3 the box adds a noindex robots meta tag to every page. Untick it, save, then use URL Inspection in Search Console to request indexing of the home page.
Google's autocomplete suggested "what is technical seo in simple words", "technical seo vs on page seo", "technical seo audit", "crawled currently not indexed how to fix", "does website speed affect seo" and "do i need sitemap xml" when we searched from Australia on 4 October 2026.
Want your site inspected?
Our free audit checks Google's three requirements on your key pages and grades what we find.