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How Do Search Engines Work? – The Process Explained

Search Engines, the Mechanism behind Internet Search

It’s almost impossible to imagine life without Internet Search. When we don’t know the answer to a question, someone is bound to say “Let’s look it up” or “Google it!”.  We type a question or some words into the search bar of a search engine and website recommendations immediately appear on our screen. We take this for granted.

But have you ever wondered how search engines actually work? How do they find the most relevant websites from all over a vast worldwide network? And how can they provide listings so instantaneously? This article will give a simple explanation of how search engines work and why it matters for you and your website.

What is a Search Engine?

OxfordLanguages gives this definition:

Search Engine – a program that searches for and identifies items in a database that correspond to keywords or characters specified by the user, used especially for finding particular sites on the World Wide Web

In other words, a search engine is a computer program. It maintains a database of words (keywords) linked to websites that use or are relevant to them, then presents you with the list of websites which it considers the best match for your search. Google, Yahoo and Bing are among the best-known search engines which you will have come across.

definition of search terms, the words used in an Internet search to tell a search engine what results to produce

An Internet Search – The Start or the End of the Process?

When we type search terms into a search bar, it may be the start of the process for us, but it’s the end of a series of steps which the search engine has already carried out.

The 3 main steps are:

  • Crawling – following links to discover pages on the World Wide Web
  • Indexing – storing information about the pages in its database
  • Ranking – presenting web page results in an order based on their relevance to the search

Below, we’ll look at those 3 steps in more detail.

Step 1 – Crawling

Search engines must work constantly to keep up with the ever-changing and growing content on the World Wide Web. So, they use automated programs referred to as web crawlers, spiders, or bots.  The crawlers constantly move around the Internet following links and reporting the pages they find for inclusion in the search engine’s database.

The crawlers also download pages which are cached in the database and produced to fulfil search requests.  So although it seems that we are searching the Internet in real time, in fact, we are looking at a recent copy of it. The advantage of this is that search results can be produced almost instantaneously.

Because crawlers work by following links, they might not quickly find new websites which are not linked from elsewhere. So, website owners can proactively request the search engine to index their site to make it visible as quickly as possible. A site map included on a website will help crawlers to index its pages and recognise changes to them over time.

It is possible to prevent parts of your website being visible to crawlers by using a robots.txt file, which instructs crawlers how to behave when crawling your site.

excerpt of a sitemap, used to help crawlers find the pages on your website
Excerpt of a sitemap
example of robots.txt file which tells crawlers how to behave on your website
robots.txt format

definition of the bad and outdated practice of keyword stuffing by including repetitive keywords on websites

Step 2 – Indexing

At indexing stage, the quality of the content found by crawlers is analysed. Criteria include whether it is up-to-date, valuable, relevant, original and authentic.  If it meets the quality standards, it will be placed in the search engine’s database and indexed. This includes linking the keywords used in a web page to its domain name.

The methods used by search engines to evaluate website content are much more sophisticated than they were in the early days of the Web.  Keyword stuffing is no longer tolerated and could lower the search results ranking of your website. Keywords must appear in a meaningful but not excessive way in your site’s text and media content.

Step 3 – Ranking

The final step carried out by the search engine is Ranking. That is, deciding the order in which the matching results will appear on the Search Engine Results Page (SERP).  This stage is all-important for businesses as high ranked listings receive many times more clicks than lower ranked ones.

Over 200 factors contribute to a web page’s rank, but in essence the top ranking pages will be the ones that the search engine’s algorithms consider to be most relevant and useful. 

Since each search engine uses its own algorithms, top rank in one search engine is no guarantee of similar ranking in another. Some search engines place their emphasis on content quality while others focus on user experience or the number of links from external sources.

Regardless of their differences, the ranking factors of all search engines fit under what are known as the “Three Pillars of SEO :

The 3 Pillars of SEO

  • Technical Optimization including loading speed, crawlability, ease of navigation, mobile-friendliness
  • On-Page Optimizationincluding trustworthiness and proven expertise in the relevant field, content tagging, inclusion of relevant keywords and images, and ease of reading
  • Off-page optimizationincluding Social Media presence and backlinking from other trusted websites


Having considered how search engines work, what are the points to take away? Here are a few suggestions:

  • Good website design and plenty of high quality content are the best way to achieve a good search results ranking.  Your site needs to be quick to load, easy to read and navigate, and provide original content which is relevant to your subject, without excessive repetition.
  • Your website should contain internal links and a sitemap to enable crawlers to find all of its pages.  If you can get other websites to include links to your site (backlinks), that will further increase your website’s authority in the view of a search engine.
  • When you make changes to your website, you should request search engines to re-index it to be sure they are recognised as quickly as possible.
  • An up to date social media presence will contribute to your website’s ranking in search engines.

We hope this article has helped you better understand search engines and how they produce results listings. If you found it useful, please feel free to share it.



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