What is SEO? How search engine optimisation works and how to improve it in 2026

SEO, or search engine optimisation, is the work of helping search engines crawl, understand and index your pages so they show them to people searching for what you offer. You do not pay Google for it. You improve it in order: first make sure Google can index your pages, then make them answer the search better than others, then work on performance.

To check it on your own site: SEO audit

What is SEO?

SEO is the set of changes to a website that make it more likely a search engine will show it in its organic results, the ones that are not adverts. The letters stand for search engine optimisation (or optimization, in American spelling). Google sums it up as helping search engines understand your content and helping users find your site1.

Two things are worth separating from the start. Organic results cannot be bought: Google states in its documentation that it does not accept payment to crawl a site more frequently or to rank it higher2. Google Ads is a separate system. This guide covers only the organic side.

Nor is there a trick that puts you at the top. Google's own SEO Starter Guide says so plainly: there are no secrets that will automatically rank your site first1. Its page on hiring an SEO adds that nobody can guarantee a number one ranking on Google3. Be wary of anyone who promises one.

SEO has four fronts that you work on at the same time:

If your business serves customers in a particular place, there is a fifth front: local SEO, built around your Google Business Profile. It is covered in the guide to local SEO in the age of AI search.

How does Google work: crawling, indexing and serving results?

Google Search works in three stages: it crawls the web to discover pages, indexes them to understand and store their content, and serves them in results when someone searches for something related. Not every page gets through all three stages, and finding out where yours stops is the first diagnosis you should make2.

Crawling: Googlebot finds and downloads your pages

Googlebot, Google's crawler, discovers new pages by following links from pages it already knows, by reading the sitemaps you submit and by returning to pages it has visited before2. An algorithm decides which sites to crawl, how often and how many pages to fetch from each. Google also renders the page with a recent version of Chrome and runs its JavaScript, because without that step it would not see content loaded that way.

Knowing about a URL does not mean Google will crawl it. According to Google, the usual reasons it does not are server or network problems, robots.txt rules that block it and pages that require you to log in2. The guide to technical SEO covers how to diagnose each one.

This is where a common mistake creeps in. robots.txt tells crawlers which URLs they may visit; it does not remove a page from Google. The documentation itself warns about this: to keep a page out of results, use noindex or password-protect it4. A URL blocked in robots.txt can still appear in results if other sites link to it.

Indexing: Google understands and stores what is there

During indexing, Google analyses the text, images, videos and tags such as <title> and the alt attribute. It also groups duplicate pages and chooses one as canonical: the representative version it may show in results2.

Google is explicit here: indexing is not guaranteed, and not every page it processes ends up in the index2. Nor does everything need to be indexed. In the Search Console help, Google advises not to expect every URL on your site to be indexed, only the canonical pages, and to make sure your important pages are5.

Since Google moved to mobile-first indexing, what counts is the mobile version: Google uses the content crawled with its smartphone agent for indexing and ranking6. If your mobile version hides text, structured data or links that the desktop version has, as far as Google is concerned they do not exist.

Serving results: relevance and hundreds of factors

When someone searches, Google picks the pages from its index that it considers most relevant and of the highest quality, using hundreds of factors that include the user's location, language and device2. That is why there is no single "position": the same query gives different results in London and in Sydney, or on a phone and on a laptop.

What factors affect SEO?

Google does not publish a list of ranking factors with their weights, so be sceptical of anyone who claims to have one. What it does publish is Google Search Essentials: a set of minimum technical requirements, spam policies and key best practices7. With that and the rest of its documentation, the factors fall into four groups.

Helpful content written for people

Helpful content is content created to serve a person, not to manipulate a search engine's rankings. It is the central idea of Google's guide to creating helpful, reliable, people-first content, updated on 5 October 20268. The guide offers self-assessment questions: whether the content provides original information, analysis or research, whether it goes beyond the obvious and whether someone would bookmark it or recommend it.

The same guide adds the "who, how and why" framework: make it clear who wrote the content, explain how it was produced (including whether automation was involved) and make sure the main reason for it is to help people8. On E-E-A-T (experience, expertise, authoritativeness and trustworthiness), Google says it is not a specific ranking factor but a mix of signals its systems use to identify content with those qualities, and that trust matters most8.

Technical access: crawling, indexing and mobile

The technical requirements are the minimum you need to compete. Google defines them as the bare minimum a page needs to be shown in Search, and warns that meeting them does not guarantee it will be crawled, indexed or served7. There are three: Googlebot is not blocked, the page works (it is not an error page) and it has indexable content9.

Internal links belong in this group. Google uses links as a signal of relevance and to find new pages, and it can only follow links that are an <a> element with an href attribute10. Its recommendation is that every page you care about has a link from at least one other page on your site.

Page experience and Core Web Vitals

Core Web Vitals are three Google metrics that measure real users' experience of a page loading, responding to input and staying visually stable. Google recommends reaching "good" on all three and says its ranking systems use them11. These are the thresholds published on web.dev12 and applied by PageSpeed Insights13:

Two details change the priorities. First, the thresholds are measured at the 75th percentile of real visits, split between mobile and desktop12. A lab result on your fast laptop is not what Google sees. Second, Google says it always tries to show the most relevant content even when its page experience is sub-par, and that there is no single page experience signal11. Speed helps, but it does not make up for content that does not answer the search. The guide to Core Web Vitals explains what each metric measures and what usually drags it down.

Authority: links and reputation

Links from other sites still count: Google uses them as a signal when working out how relevant pages are10. What you cannot do is manufacture them. The spam policies define link spam as creating links primarily to manipulate rankings, and include paying money for links, exchanging goods or services for them, or sending someone a free product in exchange for an article with a link14. Sites that break these policies, Google says, may rank lower or disappear from results altogether.

Legitimate authority is earned with content that others want to cite: original data, useful tools, guides that solve a problem better than the rest.

Which SEO myths does Google itself debunk?

Much of the SEO advice in circulation is contradicted by the official documentation. This table collects the most repeated claims, with what Google says as of 7 October 2026:

The practical upshot: the time you spend counting words or filling in tags nobody reads is better spent on the checks in the next section.

How do you improve SEO? A prioritised checklist

Improving SEO means first removing whatever stops Google from seeing your pages, and then making those pages the best possible answer. Order matters: a page that is not indexed gains nothing from any content or speed improvement.

This checklist runs from most to least urgent. You can do all of it for free with Google Search Console (Google's free tool for seeing how it crawls, indexes and shows your site) and other public tools:

If you are short on time, do rows 1 to 3 this week. They rule out the problems that cost the most traffic, and they take an afternoon.

To work through the checklist step by step, from adding your site to Search Console to setting up a Business Profile, follow the guide on how to rank a website on Google. To do it methodically across a whole site, the SEO audit guide explains how to document and prioritise each finding.

How to choose which searches to target

The checklist tells you how to get a page into shape; you still need to decide which pages to create. You have two free sources for that. The Performance report in Search Console shows the queries you already appear for, with clicks, impressions, click-through rate and average position23. A query with many impressions and few clicks usually points to a page that shows up but does not persuade.

The second source is your competitors. Looking at which pages they have, which searches they cover that you do not, and what they do better on the ones you share gives a more useful task list than any keyword tool. The guide to SEO competitor analysis explains how to do it without copying anyone.

How does SEO relate to AI search?

SEO is the foundation of visibility in AI search: an assistant that searches the web can only cite pages it can find and read. With Google the link is direct. Google says there are no additional requirements to appear in AI Overviews or AI Mode: the page must be indexed and eligible to be shown in Search with a snippet24.

That has two practical consequences:

1. An indexing problem takes you out of both. If a page is not in the index, it appears neither in the classic results nor in Google's AI answers.
2. Snippet controls also affect AI. Google states that nosnippet, max-snippet and noindex limit what is shown in its AI features24. If you restricted your snippets years ago for some other reason, that setting now also costs you visibility in AI answers.

What changes is the emphasis. In classic results the whole page competes; in an AI answer, a fragment competes (a paragraph, a table, a list) that the assistant can extract and cite. That is why AI search optimisation adds to the SEO foundation a direct answer up front, data with sources and authorship signals. Google also counts that traffic with the rest: visits from AI Overviews and AI Mode appear in the Performance report in Search Console, under the "Web" search type24.

The guide to AI search optimisation covers this second half: which AI crawlers to let in, how each assistant picks its sources and how to write so you get cited.

How do you measure SEO, and how long does it take to show?

Measuring SEO means separating two questions: where you appear (results) and why you appear or not (causes). Each has its own tool, and mixing them up produces reports that say a lot and explain little.

Results are measured with Search Console. Its Performance report gives clicks, impressions, click-through rate and average position, and lets you group them by query, page, country, device and date23. Average position is an average of your site's topmost position in each impression, so use it to spot trends, not as the exact place each user sees you.

Causes are measured by auditing the page: whether it can be crawled and indexed, whether the content answers the search, whether titles and descriptions are unique, whether performance meets the thresholds and whether the structured data is valid. That is what tells you what to fix.

How long a change takes to show

There is no fixed timeframe. Google says some changes may take effect in a few hours and others may take several months, and that in general you should wait a few weeks before judging whether a piece of work had an effect1. On URL inspection it adds that indexing a page typically takes a day or so but can take much longer, and that requesting it does not guarantee the page will enter the index18.

That is why, when someone offers you SEO, Google recommends asking what results they expect, in what timeframe and how they will measure success3. An answer with a guaranteed date and position is your cue to look elsewhere.

Where SmoothSeen fits in

This blog belongs to SmoothSeen, a website audit tool that measures visibility in search engines and AI assistants and delivers reports with the agency's branding. It works on the causes side: it reviews a page and returns two scores, search visibility and AI visibility, a comparison with up to three competitors, an action plan ordered by severity and a before-and-after comparison when you analyse again. On paid plans, the report comes as a PDF or a link, and the analysis can be repeated on a schedule.

For search visibility it checks crawling and indexing, content, speed with PageSpeed Insights (lab and field data), structured data, mobile and accessibility, security (HTTPS, mixed content, security headers, SPF, DMARC and lists of dangerous sites) and links. SmoothSeen does not track rankings in Google or connect to Search Console or Google Analytics: to see where you appear and how many clicks you get, Search Console is the source. You can see the detail in what the search visibility analysis checks.

Guides on this topic

Each guide develops one part of this one. Where to start:

• How to rank a website on Google, step by step. The exact order of tasks for a new or stalled site: Search Console, sitemap, URL inspection, content and Business Profile, without paying for ads.
• SEO audit. The method for reviewing a whole site, documenting each problem with evidence and prioritising what you find.
• SEO competitor analysis. How to choose who to compare yourself with, what to look at on their pages and how to turn the differences into tasks.

Performance and technical:

• Core Web Vitals: LCP, INP and CLS. What each metric measures, its official thresholds and the most common reasons a page falls short of "good".
• PageSpeed Insights: how to read it. The difference between field data and lab data, and which of the report's recommendations to fix first.
• Technical SEO. Crawling, indexing, canonical URLs, redirects and hreflang, with how to check each one.
• Structured data with schema.org and JSON-LD. How to mark up what the page already shows and validate it before publishing.
• Image SEO. Modern formats, lazy loading and alt text, to gain speed and help Google understand each image.
• Broken links. How to find links that lead to an error and decide whether to fix, redirect or remove them.

Content and accessibility:

• Title tag and meta description. How to write the two pieces of text searchers see, and why Google sometimes rewrites them.
• Web accessibility and SEO. Which accessibility improvements also help search engines understand the page.

Security and trust:

• HTTPS and SEO. The certificate, mixed content and what happens if your site ends up on a list of dangerous sites.
• HTTP security headers. What each header protects, how to add it without breaking the site and how to check the ones your server already sends.
• SPF, DKIM and DMARC. The three records that help stop anyone sending email while pretending to be your domain.

Frequently asked questions

What is SEO and what is it for?

SEO stands for search engine optimisation. It is the work of helping Google and other search engines crawl, understand and index your pages so that they show them in their organic results. It brings you visits from people who are already searching for what you offer, without paying for every click as you would with adverts.

What is the difference between SEO and SEM?

SEO covers the organic results, the ones you cannot pay for. SEM, search engine marketing, is usually used for paid search adverts such as Google Ads, although some people use it as an umbrella term for both. The two run on separate systems: paying for ads does not improve your organic rankings, and organic work does not lower your advertising costs.

Can you pay Google to rank first?

Not in the organic results. Google states in its documentation that it does not accept payment to crawl a site more often or to rank it higher, and that nobody can guarantee a number one ranking. What you can pay for is Google Ads, which runs as a separate system. In the Business Profile you cannot pay for a better local ranking either.

How long does SEO take to work?

There is no timeframe anyone can guarantee. Google says some changes show in hours and others take months, and advises waiting a few weeks before judging a piece of work. Fixing an indexing block can show quickly; building authority with content and links usually takes much longer. Track the trend in Search Console over several weeks rather than a single day.

Can I do SEO myself for free?

Yes, the basics. Search Console, PageSpeed Insights, the Rich Results Test and Google Business Profile are free and cover indexing, performance, structured data and local SEO. What costs you is time: writing content that answers better than your competitors. Paid tools save work, but they do not replace that content.

What to do next

Open Search Console, search site:example.com on Google with your own domain and go through the first three rows of the checklist on your most important page. If you would rather have a tool review the crawling, titles, speed, structured data and security of your page alongside your competitors', analyse it with SmoothSeen.