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If you’re brand new to the world of SEO, you’ve probably noticed that it’s a tad complex. There’s a lot that goes into good search engine optimisation, and you need to be aware of it if you want your site and content to rank well in the SERP, aka, the search engine results page!

But where do you begin if you have minimal SEO knowledge? How would you even begin to offer SEO services? Well, a good place to start is by getting a thorough understanding of what a search engine is and how search engines work.

Given that the entirety of SEO is dedicated to mastering these search tools, knowing what they are and how they work is vital to understanding the ever-changing SEO landscape. And that’s exactly what we’re going to cover in this guide!

Points we’ll touch on:

What is a search engine?

How do search engines work?

What is crawling

How often does Google crawl a site?

How to get Google to crawl your site

What is indexing

How does search engine ranking work?

What is a search engine algorithm?

How does a search engine select the results to display?

Why do I get personalised results on Google?

Ready to get started? Awesome!

Like a lot of things in SEO, search engines are complex in how they function. So, first things first, let’s get the necessary basics out the way by answering the question, “what is a search engine?”

What is a search engine?

In a nutshell, a search engine is a tool we use to find and rank information on the web relevant to our query. They’re answer machines used to discover, understand, and sort through all the fluff on the internet to display results that you’ll actually find useful; at least, that’s what they are on a surface level.

On a deeper level, search engines are made of two key parts. The index and the algorithm. You’ve probably heard of YouTube and other social media platform algorithms that determine what results are displayed to you, and search engines work in much the same way.

You have quite the choice when it comes to search engines; Google, Bing, DuckDuckGo, etc…, but as Google is the one that practically 99% of us use, we’re going to use it as our primary example throughout this guide.

But while it’s all well and good understanding the function of a search engine, you won’t get anywhere if you don’t understand how they work behind the scenes.

How do search engines work?

As we’ve pointed out, the whole point of a search engine is to deliver the most relevant results for your search. To do this, search engines like Google need to follow three key steps:

  • Crawling – Trudging through the internet for content and code and then scanning the entirety of these URLs to see if they offer good value.
  • Indexing – Taking the information provided by the crawl and using it to put approved websites into the index.
  • Ranking – Using the index’s information, combined with machine learning algorithms, to provide you with the most relevant search results when Googling.

Essentially, search engines crawl for content, place said content into a database, and when you use a search engine, this index produces a list of relevant results that are ranked in importance and relevance using an algorithm.

With this in mind, let’s now look at each of these three steps in turn so we can properly understand what they involve in the search engine process.

What is crawling?

Crawling is pretty much as it sounds and involves a search engine literally wading through all the content on the web to find out whether or not it’s valuable for users.

They do this by using bots, also called spiders. When one of these bots comes across a URL, they download these pages, scan the content, and then use the links on the page to find more pages. This repeats until they’ve crawled a site for a set period of time, at which point it will get queued for Google indexing.

Typically, these URLs are found using something called backlinks, referral links from another site, links from a prior URL on their own webpage, and sitemaps that list all the important webpages that Google should be indexing. You can even submit individual URLs for crawling in Google using the Google Search Console.

This link-hopping and locating is crucial as it’s the quickest way for these bots to find new content and add it to the index. If a page isn’t added to the index, then it won’t appear in the SERP.

One important thing to note about crawling is that pages will not necessarily be crawled in order of discovery. Instead, a bot will queue them for crawling based on factors such as:

  • The intent and quality of the page URL.
  • How old the page is.
  • How often the page has changed.

Fortunately, this means that a site’s main pages are often targeted for a crawl, helping to get the key parts of a site out there and ensuring the rest of the site is then indexed for users to view.

How often does Google crawl a site?

The rate at which Google, or any search engine for that matter, will crawl a site is based on various factors. Typically, sites that see a lot more traffic will be crawled more regularly than less well-known sites. This is to ensure the quality of these well-used sites is maintained.

Crawls could occur every few days, or potentially every few weeks, it all depends on how important the search engine values the page in question. Naturally, this means you want to make the information on your site as valuable to a user as possible.

How to get Google to crawl your site

There are a few ways you can encourage Google and other search engines to crawl your site. As mentioned, backlinks, internal links, sitemaps, and URL submissions are a good place to start, but there are a few other tricks you can use.

For starters, users can use what’s known as robot.txts, which as files located in the root directory, that suggest which parts of a site should be crawled and how quickly. This means you can get the most important pages crawled by basically shoving them in Google’s face.

Other steps that can be taken also include:

  • Ensuring your content isn’t hidden behind sign-in forms or images.
  • Having a well-thought-out site layout that looks good on mobile and desktop.
  • Implementing good navigation that makes it simple for bots and users to get around the site.
  • Eliminate old content while retaining its authority by making use of 301 redirects, taking users to new pages from old URLs for the most up-to-date information.

What is indexing?

Stage two of the search engine process is to start indexing the pages deemed valuable by the previous crawl. In basic terms, when a page is indexed, it’s organised and slotted into an incomprehensibly vast database. There are quite literally trillions of pages in Google’s index library. It’s enormous.

Search engine indexing ensures that when you search for a query on Google that, if there is any information relating to it on the web, the search engine is able to store and pull this quickly from the database thanks to its organisation and indexing.

It’s important to note that when you do make a query in a search engine, you’re actually searching the index and not the web. So, if a page does not appear in an index, then there is no way for users to find that page, no matter how hard they Google it.

To solve this, steps need to be taken to improve the overall quality of the page. These can be similar things to improving crawl potential, but can also include:

  • Correcting content errors.
  • Overhauling the content to be more informative and read better.
  • Eliminating plagiarised or repeat content.
  • Adding in meta titles and descriptions.
  • Improving keyword density.
  • Ensuring the content is new and fresh.

How does search engine ranking work?

The final step in the search engine process, and the most important one for users, is knowing how and why Google, and all search engines for that matter, rank results in the order that they do.

In truth, it’s difficult to say exactly what goes into deciding page rankings, and that’s for one key reason. The search engine algorithm.

What is a search engine algorithm?

Algorithms, for search engines and other platforms, are mind-bogglingly complex in their design and creation. The good news is, we don’t really need to know the deep technical side of things when it comes to understanding their function.

To keep things simple, all you need to know is that an algorithm is a computer program that pulls and ranks the results for your query in the most relevant order so you can easily find the information you need.

Machine learning plays a big part in this, and algorithms are able to read and interpret the intent and meaning behind a user’s query, even if it’s poorly phrased. In short, the algorithm ensures you actually look at the information you want to see.

How do search engines select the results to display?

While a search engine might know exactly what information to pull from the index thanks to the algorithm, how does it choose which to display to you? After all, there are trillions of results in Google alone.

As mentioned above, the algorithm will take into account the intent of the query. Generally speaking, there are four types of query intent, each one denoting what the user means when they Google something:

  • Informative – Usually a question relating to a topic you’re interested in.
  • Navigational – A query that lets you navigate between more specific information on the topic you’re interested in.
  • Commercial – Results often relating the comparison of products within your query.
  • Transactional – A highly specific query that allows you to quickly find what you want to buy.

Thanks to Google understanding all of these query types, the search engine can quickly gather content that will match your search terms.

As for ranking this information, this is where the second side of the algorithm comes in. Ranking factors.

For a page to rank highly, it must meet several factors that the algorithm deems relevant. There are thought to be well over 200 for Google, but several to bear in mind include:

  • Backlinks.
  • Content relevance.
  • Content freshness.
  • Content quality.
  • Content authority.
  • Page speed.
  • Mobile-friendliness


Backlinks are right at the top when it comes to determining the quality of a site, and therefore how high it ranks. Both quantity and quality of links play a role here, but quality is always prioritised over quantity.

Those sites with a few backlinks from powerful and reputable sources will be ranked much higher, as it shows other well-known sites are referencing the page.

Through this, a site receives a better domain and URL rating and page authority.

Of course, these links have to be relevant to the content as well. A bad backlink won’t help a page. For example, a carpet shampoo site being linked to a cryptocurrency site would be deemed irrelevant by a search engine.

Content relevance, freshness, and overall quality

The second, and arguably larger factor in determining ranking, is the quality of the content. For content to rank well it needs to be:

  • Relevant to both the search query and what it claims to be about.
  • Up to date with the latest information related to the topic in question.
  • Of good overall quality, being easy to scan, read, and with minimal grammatical errors (because, let’s face it, barely any of us get our grammar 100% right).

To achieve relevance, the keywords in the content must match the query, as should the content topic, so the person making the query actually gets the information that they’re after.

For freshness, the search engine will simply look at how new the content is and decide if that is a factor in the rankings too. For generic searches, it may display the most recent uploads, but for date-specific queries, it will only choose sites from that period.

And with quality, you just need to ensure that your content, be it written work, video, or design in nature, is well constructed. For written content in particular, you must make it scannable, and for design, your websites should be easily navigable by a user.

Content authority

Content authority relates to how authoritative the search engine believes the page to be in relation to a user’s query. In other words, is the content on the page factually accurate, relevant to the query, and backed up by a reputable source and links?

Page speed

While not related to topic quality per se, page speed is very important, and can be affected by the type of content you want to display. Statistically, most users won’t wait more than a few seconds for a site to load before moving on, so if a page loads fast, Google will rank it higher.

If you need to improve page speed, then you should reach out to a developer to discuss how to do this.


Nowadays, Mobile is key to ranking high in a search engine algorithm. Over 50% of all searches are now made on mobile, meaning your site needs to be mobile-friendly so users can easily navigate it.

Google actually operates on a mobile-first policy, meaning it will scroll a site’s mobile page first before moving onto its desktop version, so you want to get your mobile site right the first time.

Why do I get personalised results on Google?

You may have noticed while googling pretty much anything, that a lot of the search results you get back are in some way tailored to you. Search engines like Google can now tailor your results to more closely align with your personal preferences, getting you closer to the results you want.

These are based again on algorithmic factors, such as:

  • Repeat searches.
  • Search history.
  • Your location.
  • Your preferred language.
  • Your search settings.

These are all useful little additions that ensure the results you get for local restaurants don’t recommend you something halfway around the world or give you results in a language you can’t read.

It also means that Google can quickly give you products you might want based on what you’ve searched for previously, making everyone’s lives just that little bit easier.

And there you have it, with that boatload of information you should now have a firm grasp on the foundations of how a search engine works. There are, of course, many nuances you can learn about to bend your search engine of choice to your will, but for now, you know why Google displays its results the way it does.

If you enjoyed this guide and want to know even more about SEO and organic content creation, then be sure to check out our other guides on the c3 blog, like our ones on how to do keyword research for SEO or what is content writing?

Of course, if you want to learn more about us here at c3, our roles, and the services we provide, then why not get in touch with us today about joining the team or working with us to take your business to the next level.