How Does SEO Work

How SEO Works

Everyone knows that organic search is important to businesses and organisations of every size. Google, in particular, is in such a powerful position, that a seemingly routine algorithm update (like the Medic Update last year) has the potential to obliterate a websites traffic (and consequently, it’s revenue). But how exactly does SEO work?

How Do Search Engines Work?

In general, Search Engines including Google broadly follow a 3 step process to retrieve and display search results. The 3 key parts of this process are the:

  1. Crawler
  2. Indexer
  3. Ranker

The Web Crawler

  • Crawling is the process by which search engines discover updated content on the web, such as new sites or pages, changes to existing sites, and dead links
  • A web crawler / spider crawls the web, taking direction from previously crawled URLs and XML sitemaps
  • An XML sitemap lists a website’s important pages, making sure Google can find and crawl them all, and helping it understand your website structure

The Indexer

  • Once a search engine processes each of the pages it crawls, it compiles a massive index of all pages and the words it sees on them – essentially a database of billions of web pages.
  • This content is then organised and interpreted by the search engine’s algorithm to measure its importance compared to similar pages.
  • The Indexer can be influenced with robots meta tags which can tell crawlers in advance not to index certain pages or not to follow links on certain pages

The Ranker

  • Once a query is made by a user on Google, it will check pages within it’s index that are deemed relevant to that query; a score will be assigned to each of the relevant pages based on an algorithm consisting of hundreds of different ranking signals – and the page with the highest score will rank 1st
  • One way to influence the ranker is by building Google’s trust in your content by attracting high quality links from other trusted websites

Optimising For Search – The 3 Pillars

Rather than focusing too much on the latest hyped up tactics or fads, there are 3 core principles of SEO, that have been proven to contribute to positive SEO results over the long term. These “3 Pillars of SEO” are:

  • Technology
  • Relevance
  • Authority
the three pillars of SEO

Technology/ Technical SEO

Technical SEO optimisation concerns the technical building blocks of a website: HTML code, URL structure, HTTP status codes, XML sitemaps, etc.A website’s technology is all about making sure search engines can crawl and index all your content and in the right way. This means having clean HTML code, properly structured URLs (with no parameters, if at all possible), the right HTTP status codes for the right kind of webpages (so a Not Found page results in a 404 code, not a 200 or 302), proper XML sitemaps, etc.
In other words – Technical SEO is predominantly concerned with the Crawling aspect of the search engine process.

Technical SEO

Relevance / Content Optimisation

Content Optimisation deals with optimising title tags & meta descriptions, headings, content structure, readability, topical focus, etc.When search engines can crawl all your site’s content, that doesn’t mean they know what your content is about. The relevance aspect of SEO looks at the different elements of your content to make sure that search engines can interpret and contextualise it.Optimising title tags, headers properly structured contentand focusing on one core topic per page including the right semantic signals, etc. will ensure that Google and other search engines can understand the focus of your context and index it accordingly.
In other words – Relevance is predominantly concerned with the Indexing aspect of the search process.

Content SEO

Authority / Link Building

Authority is achieved through links and citations which indicate to search engines that your website is a trusted source.Great content alone is not enough to rank well in search results. You need to be seen as a trusted source, which is where the authority aspect comes in. With sufficient links from other trusted websites, your site will be seen as trustworthy as well and search engines will rank your content higher in search results for relevant queries.
In other words – Authority is predominantly concerned with the Ranking aspect of the search process.

Authority SEO

In Summary…

  1. Technical SEO Optimisations ensure that your site can be crawled by Google and other search engines.
  2. Content Optimisations make sure that Google and other search engines can understand the context of your site content and index it correctly.
  3. Site Authority (i.e. inbound link building) ensures that Google and other search engines trust your website, and ultimately push your content above competitors in the SERP for relevant queries.
How SEO Works

Obviously Search Engines and SEO are pretty complex and, technically speaking, all 3 steps in the Search Engine information retrieval process and the 3 Pillars of SEO Optimisation can impact upon one another in a variety of ways. However, broadly speaking these are the key relationships between both and a very useful way to make sense of the increasingly complex world of search engine optimisation.

I hope this guide has been helpful and would love any input or feedback at
If you are an Irish business owner looking for help with your SEO efforts, take a look at the SEO Consultancy section on my website to see if you think I would be a good fit for your organisation.

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darren mcmanus seo

Darren is SEO Growth Lead at Velocity Growth. He is experienced in developing bespoke SEO roadmaps and implementing long term SEO strategies to build organic visibility, traffic and conversions for clients across a diverse range of industries.