How Search Engines Work – The COMPLETE Guide To Read

A search engine’s basics are the ability to crawl the entire web using crawling bots called spiders and understand all pieces of content.

These web crawlers follow links from page to page to find new content to be indexed.

Every single moment you type in something on a search engine, content is ranked because of certain algorithms.

Search engines crawl, index, and rank every page present or found.

So, when we search for something on Google, for example, only relevant content will show up.

By learning what we will show you, you will be able to rank your pages higher on the SERP through SEO.

SEO is directly linked to search engines, so pay attention.

Without further due, in this guide, we are going to talk about the following aspects.

Search Engine’s Basics

Before we go into the technical parts of a search engine, let’s make sure you understand what is a search engine and how it works.

Search engines are tools that find and rank web content matching a user’s search query.

Every search engine has 2 main parts:

  1. Search Index – A digital library of information about web pages.
  2. Search Algorithms – Programs that rank pages based on certain criteria
search index

The most popular search engine, as you know, is Google.

However, there are others like Bing, Yahoo, or DuckDuckGo.

By ranking pages based on their algorithms, search engines aim to provide the user with the best and most relevant results.

Also, there are 2 types of search results:

  1. Organic results
  2. Paid results

Here’s a short comparison between both.

search traffic

So, websites that appear to have Ads on Google, on the top-ranking page, are paying to be there.

That’s how search engines make money.

If you haven’t figured it out yet, we are talking about PPC right now.

So, whenever someone clicks an Ad, the company has to pay Google a certain amount of money for receiving that click.

It’s market share, basically.

The more people click on Ads, the more money Google makes.

Understanding how search engines find, index, and rank content will help you to rank your website in organic search results for relevant and popular keywords.

If you can rank high for these queries, you’ll get more clicks and organic traffic to your content.

Right now, Google has a 92% market share, making it the most used search engine.

google market share

Google is the search engine that most SEO professionals and website owners care about because it has the potential to send more traffic their way than any other search engine.

search engine market share

Search Engine’s Index

Most well-known search engines like Google and Bing have trillions of pages in their search indexes.

So before we talk about ranking algorithms, let’s see how to build and maintain a web index.

Here’s the basic process, courtesy of Google:

Let’s break this down, step by step:

  1. URLs
  2. Crawling
  3. Processing & rendering
  4. Indexing

The process below applies specifically to Google, but it’s likely very similar for other web search engines.

1. URLs

search engine URL

Everything begins with URLs.

Google discovers these through various processes, but the three most common ones are:

  • From backlinks – Google already has an index containing trillions of web pages. If someone adds a link to one of your pages from one of those web pages, they can find it from there.
  • From sitemaps – Sitemaps list all of the important pages on your website. If you submit your sitemap to Google, it may help them discover your website faster.
  • From URL submissions – Google also allows submissions of individual URLs via Google Search Console.

2. Crawling

web crawler

Crawling is when a web spider visits and downloads a discovered page.

It’s important to note that Google doesn’t always crawl pages in the order they discover them.

Google queues URLs for crawling based on a few factors, including:

  • PageRank of the URL
  • How often the URL changes
  • Whether or not it’s new

This is important because it means that search engines might crawl and index some of your pages before others.

If you have a large website, it may take a while.

3. Processing

At this stage, Google works to understand and extract key information from the crawled pages.

Nobody outside of Google knows every detail about this process, but the important parts for our understanding are extracting links and storing content for indexing.

Google has to render pages to fully process them, which is where Google runs the page’s code to understand how it looks for users.

4. Indexing


The processed information from crawled pages is added to a big database called the search index.

This is essentially a digital library of trillions of web pages where Google’s search results come from.

When you type a query into a search engine, you’re not directly searching the internet for matching results.

You’re searching a search engine’s index of web pages.

If a web page isn’t in the search index, search engine users won’t find it.

That’s why getting your website indexed in major search engines is so important.

How Search Engines rank pages

Discovering, crawling, and indexing content is merely the first part of the puzzle.

Search engines also need a way to rank matching results when a user performs a search.

This is the job of search engine algorithms.

Each search engine has unique algorithms for ranking web pages.

But as Google is by far the most widely used search engine, that’s the one we’re going to focus on throughout the rest of this guide.

Google famously has +200 ranking factors.

Nobody knows what all of these ranking factors are, but we do know about the key ones.

Let’s discuss a few of them.

  • Backlinks
  • Relevance
  • Freshness
  • Topical authority
  • Page speed
  • Mobile-friendly
how search engine works

Backlinks are one of Google’s most important ranking factors.

The two most important ranking factors are content and links.

So, write quality content to gain backlinks, links pointing to your website.

Links have been an important ranking factor in Google since 1997 when they introduced PageRank.

There is a clear correlation between the number of websites linking to a page and the amount of organic traffic it gets from Google.

However, it’s not all about quantity because not all backlinks are created equal.

It’s perfectly possible for a page with a few high-quality backlinks to outrank a page with lots of lower-quality backlinks.

There are six key attributes of a good backlink.

These are:

  1. Link authority
  2. Link relevance
  3. Anchor text
  4. Follow vs No-follow
  5. Placement
  6. Destination

2. Relevance

search engine

Google has many ways of determining page relevance.

At the most basic level, it looks for pages containing the same keywords as the search query.

But relevance goes way beyond keyword matching.

Google also uses interaction data to assess whether search results are relevant to queries.

In other words, are searchers finding the page useful?

This is partly why all of the top results for “apple” are about the technology company, not the fruit.

Google knows from interaction data that most searchers are looking for information about the former, not the letter.

Interaction data is far from the only way Google does this, though.

Google has invested in many technologies to help understand the relationships between entities like people, places, and things.

The Knowledge Graph is one of these technologies, which is essentially a huge knowledge base of entities and the relationships between them.

Both Apple (fruit) and Apple (technology company) are entities in the Knowledge Graph.

Google uses the relationships between entities to better understand page relevance.

A matching result for “apple” that talks about oranges and bananas are clearly about the fruit.

But one that talks about iPhone, iPad, and iOS is clearly about the technology company.

It’s in part thanks to the Knowledge Graph that Google can go beyond keyword matching.

Sometimes you may even see search results that fail to mention seemingly important keywords from the query.

For example, take the second result for “apple paper app,” which doesn’t mention the word “apple” anywhere on the page.

Google can tell it’s a relevant result partly because it mentions entities like iPhone and iPad that are undoubtedly closely related to Apple in the Knowledge Graph.

3. Freshness

Freshness is a query-dependant ranking factor, meaning that it matters for some results more than others.

For a query like “what’s new on amazon prime,” freshness is important because searchers want to know about recently-added movies and TV shows.

That’s likely why Google ranks newly published or updated search results higher.

4. Authority on topic

authority on topic

Google wants to rank content from websites with authority on the topic.

This means that Google might view a website as a good source of results for queries about one topic but not another.

5. Page speed

search engine

Nobody likes waiting for pages to load, and Google knows it. 

Many people get hung up about page speed, so it’s worth noting that your pages don’t need to be lightning-fast to rank.

Google says that page speed is only a problem for pages that “deliver the slowest experience to users.”

In other words, shaving a few milliseconds off a site that’s already fast is unlikely to boost rankings.

It just needs to be fast enough not to negatively impact users.

You can check the speed of any web page in PageSpeed Insights, which also generates suggestions to make the page faster.

PageSpeed Insights also shows how your page fares when it comes to Core Web Vitals.

Core Web Vitals are made up of three metrics that assess the loading performance, interactivity, and visual stability of your web pages.

You can see the performance of all pages on your website using the Core Web Vitals report in Google Search Console.

6. Mobile-friendly

search engine

65% of Google searches happen on mobile devices.

That’s why mobile-friendliness has become a top-ranking factor.

Mobile-friendliness is also a ranking factor for desktop searches thanks to Google’s switch to mobile-first indexing.

This means that Google “predominantly uses the mobile version of the content for indexing and ranking” across all devices.

In other words, a lack of mobile-friendliness can affect rankings—everywhere.

You can check the mobile-friendliness of any web page using Google’s Mobile-Friendly Test tool.

How search engines personalize search results

search engine results

Search engines understand that different results appeal to different people.

That’s why they tailor their results for each user.

If you’ve ever searched for the same thing on multiple devices or browsers, you’ve probably seen the effects of this personalization.

Results often show up in different positions depending on various factors.

It’s because of this personalization that if you’re doing SEO, you’re better off using dedicated tools to track ranking positions.

How do search engines personalize results?

Google states that “information such as your location, past search history and search settings all help [us] to tailor your results to what is most useful and relevant for you at that moment.”

So, Google personalizes search results by:

  1. Location
  2. Language
  3. Search history

Search engines and SEO

Understanding how search engines work is the first step towards ranking higher in Google and getting more traffic.

When search engines can’t find, crawl and index your pages, you can’t grow your web presence.

If you want to know how SEO works, or simply want to find out some tips & tricks, feel free to read our SEO Guide.

So, to rank higher in Google, you must know SEO and how all this process works.

Let’s start over, but take a short way this time:

search engine basics

Now, I hope you understood how search engines work.

By the way, for any questions feel free to use the comments section down below.


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