Search engines work in three stages. First, automated crawlers such as Googlebot discover pages by following links and reading sitemaps. Next, the search engine processes what it finds and stores it in a huge database called the index. Finally, when someone searches, ranking systems pick the most relevant, helpful pages from that index and put them in order.
Internet search engines work continuously, collect information from the world’s websites, and organize that information to make it easy to find.
The process is simple from the outside: Here you type in a keyword, and you get a list of relevant pages but there are a few more steps that allow Google to show relevant results.
Let’s begin with the basics:
Key takeaways
- Search engines work in three stages: crawling, indexing and ranking, which Google calls serving results.
- Google discovers URLs through links, XML sitemaps and URL submissions in Search Console.
- Google's index covers hundreds of billions of pages, and a page that is not indexed cannot appear in results.
- robots.txt controls crawling, while a noindex tag is what keeps a page out of Google's index.
- Google ranks results on meaning, relevance, quality, usability and context such as location.
- Pages must be indexed and snippet-eligible to appear as links in AI Overviews and AI Mode.
What Is a Search Engine?
Search engines are the tools that allow a user to search for a query. The content on SERP is then matched with the most relevant results.
Major search engines like Google, Bing, and Yahoo consist of two main parts:
Search index. A search index helps users find information quickly on a website. It is a digital library consisting of information about web pages.
Search algorithm(s). Search algorithms are computer program(s) that rank matching results from the search index.
What Is the Aim of a Search Engine?
Search engines often change their ranking algorithms (the programs that rank results) to improve the answers people get.
Every popular search engine aims to understand the way users search to show them the best answer to their search queries typed on the search bar. This means giving higher priority to the highest quality and most relevant webpage of a website.
How Do Search Engines Make Money?
Google provides two types of search results:
1. Organic search results
This comes directly from the search index and you don’t have to pay anything here. Search results are listed based on relevancy to the keyword.
2. Paid search results
These come from advertisements that businesses pay for. On Google they are bought through Google Ads, which was called AdWords until 2018.
Whenever a person clicks on a paid search result, the advertiser pays the search engine. This process is known as pay-per-click (PPC) advertising.
How Do Search Engines Work?
Search engines crawl, index, and rank content that helps you to rank your website in organic search results often referred to as SERPs for popular and relevant search terms or keywords.
Google’s search engine crawler works in this 3 step process:
A. Crawling
A crawler, such as Google’s crawler, Googlebot, is a program every search engine uses to discover pages. The crawler visits a URL(website) it finds, collects all the website’s content, and stores it in the database. It even stores all the external and internal links to the website.
B. Indexing
In this process Google stores and organizes the content found during the crawling process. Once a page is indexed, it is then considered to be displayed as a result of the relevant user query.
C. Ranking
Ranking provides the piece of content that will be the best answer to a searcher’s query or search term. The search results are ordered from the most relevant to the least relevant.
So how does a search engine decide the most relevant result?
Based on the guidelines set forth by Google, these are the few things that are checked
Step 1. How Does Google Discover URLs?
The first step begins with discovering a known list of URLs. This can be done using the following methods:
a. From backlinks.
Backlinks are also known as inbound links. These are the links from one website to a webpage on another website.
According to Google, its search index covers hundreds of billions of web pages. If someone adds a link to one of your web pages by hyperlinking it on one of their articles or pages, Google considers that link a credible source of information.
b. From sitemaps.
Sitemaps contain a list of all of the important web pages on your website. When you submit your sitemap to Google, it helps them discover your website faster. Search engine submission can be easily done by submitting a sitemap to the search console.
c. From URL submissions.
Google also allows the submission of individual URLs through Google Search Console.
Step 2. Crawling
Search engine crawlers are a program used by search engines to collect data from the internet. Crawling a website usually starts with its robots.txt file, which tells crawlers which URLs they can access on the site.
The robots.txt file may also contain relevant content about sitemaps.
Google crawls the pages and queues URLs for crawling based on a few factors, that includes:
- Page Rank of the URL;
- how frequent the URL changes;
- whether the URL is new or not.
Step 3. Processing
In processing, Google works to understand and draws out relevant information from crawled pages.
In this process, Google extracts the links and stores the content for indexing.
Google has to render web pages to completely process them, to understand how it looks for users.
Step 4. Indexing
The indexing process is adding the processed information from crawled pages to a big database called the search index. The search index is a digital library of hundreds of billions of web pages from where you get Google’s search results for a relevant query.
When you type a query into Google’s search bar, you’re searching Google’s index of web pages. If a web page is not present in the search index, search engine users will never find it.
Therefore, getting your website indexed in major search engines like Google and Bing is important.
There is also a situation where a URL is not indexed by Google. This may be due to:
- Robots.txt rules: this file tells Google which pages it shouldn’t crawl. It is not a reliable way to keep a page out of Google, though, so use a noindex tag for that.
- Restrictions on a page can notify Google not to index a particular webpage (noindex tag) or to index another similar webpage (canonical tag).
- Search engine algorithms declare the webpage to be of low quality, or containing duplicate content.
- The URL shows an error page (e.g. a 404 Not Found)
How Can You Help Google Crawl and Index Your Site?
You can’t force a search engine to rank a page, but you can remove the obstacles that stop it from being found. Work through this checklist for any page that matters to your business:
- Verify your site in Google Search Console. It is free and shows which pages are indexed and why others are not.
- Submit an XML sitemap. List your important URLs so Google can discover new and updated pages faster.
- Inspect key URLs. The URL Inspection tool shows whether a page is indexed and lets you request a recrawl after a big change. Google notes that crawling can take a few days to a few weeks.
- Check robots.txt and noindex tags. Make sure you are not blocking pages you want found. Robots.txt controls crawling, while a noindex tag keeps a page out of the index.
- Link to every important page. Pages with no internal links (orphan pages) are hard for crawlers to find.
- Fix broken links and duplicates. Redirect pages that have moved, and use canonical tags where several URLs show the same content.
- Make sure the mobile version is complete. With mobile-first indexing, content that is missing on mobile may not be indexed at all.
The same index also feeds Google’s AI features. Google says a page must be indexed and eligible to show with a snippet to appear as a link in AI Overviews or AI Mode, so these basics matter for AI visibility too. Our guide to technical SEO covers each step in more depth.
How Do Search Engines Rank Pages?
Once the discovering, crawling, and indexing of content is completed, search engines need to perform search engine ranking. They order the matching pages by how well each one fits what the searcher wants.
Every search engine has its own ranking algorithms. Google says its systems look at the meaning of the query, the relevance and quality of content, the usability of pages and context such as your location and settings. Some of the key ranking factors are:
1. Backlinks
Backlinks are one of the most important ranking factors for search engines.
The quantity of backlinks doesn’t matter because not all backlinks are created equal. It’s even possible for a page with a few high-quality backlinks to outrank a page with lots of lower-quality backlinks.
A good backlink is attributed to the following factors:
- Link authority
Backlinks from authoritative websites create a strong impact on rankings. Authoritative web pages and websites are those that have many backlinks.
In Ahrefs, there are two metrics to estimate the relative authority of websites and web pages:
- Domain Rating (DR): This shows the relative authority of a website on a scale from 0 to 100.
- URL Rating (UR): This indicates the relative authority of a webpage on a scale from 0 to 100.
- Link relevance:
Link relevancy refers to how useful and topically similar a website is when they link to your website. Links from relevant websites and web pages are valuable for ranking.
2. Relevance
Search engines first judge relevance by checking whether a page contains the same keywords as the search query, and they also match synonyms and the meaning behind the words.
Google uses interaction data to evaluate whether search results are relevant to queries.
3. Freshness
Fresh content is content that has been published recently. The freshness of content is a query-dependent ranking factor. For news and fast-changing topics, Google tends to favour recently published or updated pages, while for evergreen questions freshness matters much less.
4. Page speed
Page speed is the measurement of how fast the content on your webpage loads. Page speed is also a ranking factor, and Google measures it through Core Web Vitals: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness (it replaced First Input Delay in March 2024) and Cumulative Layout Shift for visual stability.
You can check the performance of all web pages of your website using the Core Web Vitals reports in Google Search Console.
5. Mobile-friendliness
Most of the Google searches happen on mobile devices. That’s why mobile friendliness has been a major factor when it comes to SEO. Google uses mobile-first indexing, which means it uses the mobile version of your content for indexing and ranking, so a site that works poorly on phones can lose rankings.
How Do Search Engines Personalise Results?
Search engines tailor results to each user because different results suit different people.
A personalized search result is the web search results that have been tailored specifically to an individual’s interests.
According to Google the information such as your location, language, past search history and search settings help them to customize the results to what is most useful and relevant for a user at a particular moment.
Understanding how search engines work is the first step to ranking higher in Google and getting more organic traffic. Website owners use search engine optimisation (SEO) to improve the chances of their content ranking higher in Google.
Conclusion
If you have any questions mention them in the comment section below and we will be happy to discuss them.
Additionally check out our guides on digital marketing, keywords & how to use the keywords in your content.
In summary, search engines are essential resources in the digital age because they help users find pertinent information on the vast expanse of the internet. Their main goal is to efficiently satisfy user queries by offering precise, fast, and customised search results. Search engines use algorithms to rank pages according to relevance and authority; advertising is how they primarily make money.Â
Additionally, they use personalisation strategies to adjust results based on user preferences. To maximise their online presence and visibility in search results, businesses and individuals need to understand how search engines operate and how they rank pages.
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