Technical SEO
Guide

What is technical SEO?

Technical SEO covers the behind-the-scenes elements of a website that affect how search engines crawl, index, and evaluate it. Unlike content or links, technical factors are largely invisible to users - but they have a massive impact on whether your pages can rank at all.

Think of technical SEO as the foundation: content and links are the structure built on top. A weak foundation limits how high you can build.

Crawlability and indexation

Before a page can rank, Google must be able to find, crawl, and index it. Common issues that prevent this:

Robots.txt misconfiguration

A poorly-configured robots.txt can accidentally block Google from crawling important pages. Always verify your robots.txt at yourdomain.com/robots.txt after any major site change.

Noindex tags

Pages with <meta name="robots" content="noindex"> are excluded from Google's index. Check for unintentional noindex tags - they're a surprisingly common cause of ranking drops after site migrations.

Crawl budget waste

Large sites with infinite scroll, faceted navigation, or parameter-heavy URLs can exhaust Google's crawl budget on unimportant pages, leaving key pages unindexed. Canonical tags, robots.txt, and sitemap management address this.

The 2MB fetch limit

Google documented this properly for the first time in March 2026: Googlebot fetches a maximum of 2MB per URL, including the HTTP header (64MB for PDFs). The important part is what happens when you exceed it. Googlebot does not reject the page - it truncates at 2MB and passes the truncated bytes to indexing and rendering as if they were the complete document.

That failure mode is silent. A bloated page with inline scripts or base64 images ahead of the content can have its actual content cut off mid-document, and nothing in Search Console will tell you. If a page is inexplicably not ranking for content that is plainly on it, check the raw HTML size before anything else.

Core Web Vitals

Google uses three user experience metrics as ranking signals:

Largest Contentful Paint (LCP)

Measures how long the largest visible element (usually a hero image or headline) takes to render. Good: under 2.5 seconds. Common fixes: optimise images (WebP format, lazy loading, proper sizing), improve server response times, eliminate render-blocking resources.

Interaction to Next Paint (INP)

Replaced First Input Delay in 2024. Measures the time from user interaction to the page's next visual update. Good: under 200ms. Most often a JavaScript performance issue - excessive main thread work, large event handler scripts.

Cumulative Layout Shift (CLS)

Measures unexpected layout movement as the page loads - elements jumping around, buttons shifting. Good: under 0.1. Caused by images without explicit dimensions, dynamically injected content, web fonts loading late.

Structured data (Schema markup)

Structured data helps Google understand what type of content a page contains - and can produce rich results (star ratings, breadcrumbs, product details) in search listings. Google has been pruning this list hard: FAQ rich results were retired in May 2026, and Book Actions, Course Info, ClaimReview, Estimated Salary, Learning Video, Special Announcement, Vehicle Listing, Practice Problems and Dataset were all phased out from June 2025. Existing markup for a retired type causes no harm - it simply no longer earns anything. Google has also been adding: loyalty programs (2025), an expanded shipping and returns policy (2025), and merchant listing additions through 2026. Check the current documentation before building for a rich result, because this list moves. Key schemas to implement:

• Organization - your brand details, logo, contact info
• WebSite - site name, URL, search box
• Article / BlogPosting - for all content pages
• FAQ - for pages with question-and-answer content
• BreadcrumbList - for navigation context
• Product / Service - for commercial pages
• HowTo - for instructional content

What you do NOT need for AI search

This section exists because the opposite advice is everywhere, and it is wrong. Google's AI optimization guidance is explicit that AI features are built on core Search ranking and quality systems, so there is no separate technical setup for them. Specifically, Google says you do not need:

• An llms.txt file. Google documented in June 2026 that it does not use llms.txt and ignores it for Search, including AI features. It is not a ranking signal and it is not on a roadmap.
• AI-specific structured data or markup. No special schema exists for AI Overviews or AI Mode. Your existing structured data still governs rich-result eligibility, and that is its job.
• Content "chunking" or Markdown rewriting. Google has said plainly that reformatting content for machine consumption is unnecessary.
• Pages built per AI-generated sub-query. AI Mode does fan out into related queries behind the scenes, but Google explicitly warns against mass-producing pages to target them - that is scaled content abuse.

If a vendor is selling you any of the above as AEO or GEO work, they are selling you something Google says has no effect. Google added guidance in June 2026 telling site owners to check exactly this before hiring.

HTTPS and security

HTTPS is a confirmed Google ranking factor. Any site still on HTTP is at a disadvantage and will display "Not Secure" warnings in Chrome. Migration to HTTPS requires proper 301 redirect handling - every HTTP URL should redirect to its HTTPS equivalent.

Mobile optimisation

Google uses mobile-first indexing - the mobile version of your site is what it uses to determine rankings. Critical requirements:

• Responsive design that works at 375px viewport width
• No content hidden on mobile that's visible on desktop
• Tap targets (buttons, links) at least 44x44px
• No intrusive interstitials (pop-ups that cover main content on mobile)

Quick technical audit checklist

• Google Search Console: zero manual actions, no coverage errors on important pages
• PageSpeed Insights: LCP <2.5s, INP <200ms, CLS <0.1 on mobile
• All key pages indexed (check with site: operator)
• robots.txt allows Google to crawl all important sections
• XML sitemap submitted and up-to-date
• HTTPS on all pages, all redirecting correctly
• Organisation and Article schema on homepage and blog posts
• No duplicate title tags or meta descriptions