What is technical SEO? A plain-English guide
Technical SEO is the foundation the rest of your SEO stands on: the behind-the-scenes setup that lets search engines find your pages, understand them, and trust them. Great content will not rank if the technical basics are broken. The good news is that most of it is set up once and then maintained, and a well-built site handles much of it by default. This guide explains how it works and what to check.
Crawl, index, rank: three separate steps
Ranking is the last of three steps, and most technical problems happen in the first two.
- Crawling. Google's bots follow links to discover pages. A clear internal-linking structure and an XML sitemap help them find all of yours.
- Indexing. After crawling, Google decides whether to store the page in its index. Thin, duplicate, or blocked pages may not be indexed, and a page that is not indexed cannot rank.
- Ranking. Only indexed pages compete for positions.
This is why a brand-new page does not appear instantly, and why "my page is not ranking" and "my page is not indexed" are different problems with different fixes.
Check what is indexed
Checking indexation is a quick habit worth having, especially after a launch or a change.
- Search for site:yourdomain.com to see roughly what Google has.
- In Google Search Console, use URL Inspection for a specific page, and the Pages report to see what is indexed, what is not, and the reason.
If pages are missing, check that they are not blocked or set to noindex, that they are in your sitemap, that other pages link to them, and that they are good enough to be worth indexing.
robots.txt
The robots.txt file is a small text file at the root of your site that tells crawlers which areas they may or may not crawl. It can keep crawlers out of admin areas and point them to your sitemap.
Two things catch people out. The first is blocking too much: a stray rule that blocks your whole site stops it being crawled at all, so if traffic vanishes, check robots.txt early. The second is confusing blocking with removing. Blocking a page from crawling does not reliably keep it out of the index, and a page you want excluded needs a noindex instruction that Google is allowed to crawl in order to see.
Crawl budget: usually not your problem
Crawl budget is the amount of crawling Google will do on your site in a given period. It worries small businesses unnecessarily. It matters mainly for very large sites with enormous numbers of pages. A typical business site with dozens or a few hundred pages will be crawled without trouble. Avoiding thin and duplicate pages and keeping a clean sitemap is good practice regardless.
Status codes
Every page request returns a three-digit code describing what happened.
- 200: fine, the page loaded.
- 301 and 308: permanent redirect, the page has moved for good.
- 302 and 307: temporary redirect.
- 404: not found. 410: gone for good.
- 500: server error, something broke.
Broken 404s frustrate visitors, missing redirects lose what a page had earned after a move, and persistent 500 errors can get pages dropped.
Redirects
A redirect sends someone from one address to another, and they are essential whenever URLs change. A permanent redirect (301 or 308) tells Google the move is for good, so it should replace the old address with the new one in its index and carry the page's signals across. A temporary one (302 or 307) says the original will return, so Google may keep the old address.
The classic case is a redesign: every old URL should permanently redirect to its closest new equivalent, one hop, to the page that actually matches. Missing redirects are one of the commonest ways a redesign loses traffic. Redirecting everything to the homepage is not a substitute, because Google treats irrelevant redirects as errors.
Canonical tags and duplicate content
Duplicate content means the same or very similar text at more than one address. It rarely earns a penalty, but it confuses search engines about which version to rank, and that can hold your visibility back.
- It sneaks in through near-identical pages made by swapping a place name, product descriptions copied across pages, and the same site loading at several addresses.
- A canonical tag tells search engines which version is the preferred one, consolidating signals onto it.
- The fix is to make each page genuinely distinct, use canonicals where duplicates are unavoidable, and keep one consistent URL structure.
www or non-www
Whether your site lives at www.yoursite.com or yoursite.com matters far less than being consistent. Pick one, redirect the other to it, and make sure only one is indexed. If both load without redirecting, Google sees two copies of your site.
Fixing crawl errors
Search Console reports the problems Google meets, in the Pages report. The common ones are pages returning 404 that should exist, server errors, pages blocked by robots or noindex by mistake, and broken redirects or long redirect chains. Fix or redirect the broken URLs, unblock anything wrongly excluded, resolve the server errors, then use Validate fix so Google re-checks. Clearing these regularly keeps a site fully indexable.
Also part of technical SEO
Speed and Core Web Vitals, mobile-friendliness, HTTPS, clean URLs, and structured data all sit alongside the above, and each has its own guide. If you want a quick order of operations: confirm the site is indexable, confirm one URL version and clean redirects, fix any errors in Search Console, then work on speed and structure.