What Is Technical SEO? A Plain-English Guide for Business Owners

When you talk to an SEO agency, “Technical SEO” comes up constantly. The question: how deep does a non-developer business owner need to go?

The answer: the 5 topics in this article — enough to have real conversations and check whether an agency is actually doing the work.

Technical SEO — Short Definition

Technical SEO = making sure Google can reach your site (Crawl) + store it (Index) + understand it (Schema) + load it quickly (Core Web Vitals) + render it on every device (Mobile).

Where On-Page SEO is content and Off-Page SEO is backlinks, Technical SEO is the infrastructure that lets both function.

The 5 Core Topics of Technical SEO

1. Crawlability — Can Google Reach Your Site?

Google has a bot called Googlebot that “walks” your site to read content. If the bot can’t reach a page, that page won’t be indexed = it won’t appear in Google.

Things that block crawling:

robots.txt that disallows important pages
Meta tag <meta name="robots" content="noindex">
Login required (bots can’t enter passwords)
JavaScript-heavy sites the bot can’t render

How to check:

Open Google Search Console → URL Inspection → see crawl status
Open yourdomain.com/robots.txt and read the rules

2. Indexability — Does Google Keep Your Pages?

Even if Google can crawl, it doesn’t mean every page gets indexed. Google indexes pages that are high quality and not duplicates.

Things that prevent indexing:

Duplicate content — pages over 60% similar to others
Thin content — low word count, no value
Canonical conflicts — incorrectly set canonical tags
Low quality signals — users bounce quickly

How to check:

Search site:yourdomain.com and see how many pages are indexed
Compare with the number of pages in your sitemap
The numbers should be close. If they differ by more than 30%, there’s an issue.

3. Core Web Vitals — Does Your Site Load Fast Enough?

Google uses three metrics to measure user experience:

LCP (Largest Contentful Paint) < 2.5 seconds — when the main image/heading finishes loading
CLS (Cumulative Layout Shift) < 0.1 — how much the layout shifts on its own
INP (Interaction to Next Paint) < 200ms — how fast the page responds to taps

Test for free at PageSpeed Insights.

Deep dive: Core Web Vitals Guide.

4. Mobile-First — Is It Good on Phones?

Google has indexed mobile-first since 2021. If your site is great on desktop but bad on mobile → rankings suffer.

Must-haves:

Responsive design that adapts to screen size
Buttons large enough to thumb-tap (44×44 px minimum)
Text readable without zoom (16px+ on mobile)
No horizontal scroll
Forms easy to fill

5. Structured Data (Schema) — Does Google Understand Your Page?

Schema.org is the “shared language” that tells Google whether a page is a Product, Article, FAQ, Recipe, Hotel, etc.

Google uses Schema to:

Show Rich Results (star ratings, price, image carousels)
Understand context → send traffic that matches intent

Deep dive: Schema Markup Guide.

How Good Agencies vs Bad Agencies Approach Technical SEO

Aspect	Good Agency	Bad Agency
Crawl	Monthly Screaming Frog audit	Never checks
Core Web Vitals	Optimizes at the code level	Installs “WP Rocket” plugin and calls it done
Schema	Writes page-specific JSON-LD	Uses a generic plugin
Mobile	Tests on real devices	Tests in Chrome DevTools only
HTTPS	Configures HSTS + security headers	Installs SSL and stops
Sitemap	Custom logic with priorities	Auto-generates every page
Reporting	Live dashboard + insights	Monthly PDF screenshots

Where to Start Fixing Technical SEO — Priority Order

Set up Google Search Console + Google Analytics (free).
Run PageSpeed Insights to see Core Web Vitals.
Submit a sitemap in GSC.
Check Coverage Errors in GSC.
Run Mobile-Friendly Test.
Add Schema.org at minimum Organization + LocalBusiness.
Check for duplicate content using Siteliner (free).

If those 7 items are fixed and the site still underperforms = you need a deep audit.

Request a Technical SEO Audit

See our SEO Audit service — starts at 30,000 THB for sites with ≤ 100 pages.

Includes:

Full crawl + crawl budget analysis
Core Web Vitals optimization plan
Schema.org implementation plan
Mobile UX audit
An action plan your team can execute
1-hour consulting session