How Do Search Engines Work?

How Do Search Engines Work?

Ashkar Gomez
11min read
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Search engines work by crawling billions of web pages using their bot or crawlers. These crawlers are also known as web spiders; they navigate to webpages by the links attached to any page it crawls. This process discovers new pages or content and places those web pages in the search index. 

When a user searches with any query, search engines look at multiple web pages from their index database that are most relevant to the intent. Finally, rank them following the search engine algorithm.

When you find any search engine’s ranking process or system complicated, you should be expertise in how search engines work? How do they crawl, index, render, and rank?

Google is one of the fully automated search engines that use software known as web crawlers that explore the web regularly to find sites to add to our index.

In this article, we will also take you through the concept of crawl budget, crawl priority, and Page Rank. Before that, you should know the basics and working process of the search engines.

What Is a Search Engine?

Search engines are programmed software accessible worldwide with the help of the internet to get relevant information. It acts as a connecting bridge between content consumers and content creators.

Search engines are answering machines optimized with algorithms to rank the best, relevant, and fresh content. These algorithms are programmed by technologies like machine learning (ML) and artificial intelligence (AI).

In recent times, search engines have advanced to answer voice web searches. There are multiple players in the search engine market, yet Google holds a market share of 91.47%.

search engines available

Here is the market share of other search engines available:

  • Bing – 3.42%
  • Yahoo – 1.1%
  • Baidu – 0.83%
  • Yandex – 1.78%
  • DuckDuckGo – 0.54%
  • Others – 0.86%

Search engines use three basic mechanisms:

  • Web crawlers: Bots or web spiders that constantly browse the web to find new content. By using hyperlinks, crawlers can hop to other pages and index them.
  • Search index: It is a database that collects all web pages’ information and organizes that with relevant keywords when a query arises. Search engines Rank only the quality content from their index. Also, other factors decide the ranking of web pages.
  • Search algorithms: A set of frameworks that determines the quality of web pages, their relevancy to a search term, and ranking results based on quality and popularity.

Search engines always try to provide the information that can drive more number of user and retain them. Quality information with authentication can bring as many online users and spend more time. These search engines earn by search engine marketing (SEM) like Pay Per Click (PPC), Display Ads, etc. 

When online users trust a search engine and spend quality time, search engines can target them with ads that convert. Google, the leading search engine, earned almost $147 Billion in 2020 from Google Ads, which is 80% of the total revenue of Alphabet.

How Do Search Engines Work - A Step by Step Approach:

The search engines generally work with three processes that help the searcher to get the relevant page. They are

  • Crawling – Search engines use automated programs called crawlers to pick up the text, images, and video from web pages.
  • Indexing – Search engines extract information from pages, including text, images, and video files, and store them in a database known as the search engine index.
  • Ranking – When a user types in a query, search engines display relevant results to the query.

Let’s decode every function in detail.

What Is Search Engine Crawling?

How Google Search engine crawls - What is Crawling

The first phase of the search engine’s work is discovering web pages, content, and multimedia. This process is known as “URL Discovery” as per the Google search engine.

Usually, the discovery happens when a new page or post is linked to an existing page that is a known page or indexed page. If not, search engines discover them through the sitemap.

Discovery doesn’t mean crawling. Once the URL is discovered, search engines send their crawlers (e.g., Googlebot) to understand the content, multimedia, links, and HTML tags used. This process is known as crawling.

Search engines use ample super-fast computers to crawl billions of web pages over the internet. The search engine crawlers use algorithms to define which website to crawl, set crawl budget, and crawl priority.

Crawl Budget – How many web pages (URL) to crawl in a particular interval?

Crawl Priority – What are the web pages to crawl, setting a rank with a highest of 1 to a lowest of 0.1?

These crawlers don’t crawl all the web pages they discover; they work by a few frameworks. Crawlers of Google search engines are programmed only to crawl the page with a rapid loading speed. The slow web pages will return with HTTP response code 500.

During crawling, search engines render the web page and run JavaScript (js files). Rendering is a vital function of search engines. In a few cases, websites rely on JavaScript codes to fetch the web page’s content.

The website disallows crawling under a few circumstances like the following:

  • Blocking by Robots.txt
  • Disallow by Robots Tag
  • Web pages might not be accessible without a login to the website
  • Duplicate content without proper canonical tag
  • Internal Server issues
  • Bad HTTP response codes like 4xx, 5xx

The following reasons could inhibit your website from crawling:

  • Brand New website – In this case, crawling has not yet started
  • No external websites referring to your websites (Backlinks)
  • Orphaned page – No referring internal pages
  • Penalized by Google search engine for spammy practices
  • Low count of content
  • Cloaking Content – Text is hidden behind Non-text content like images, videos, GIFs, forms, etc.
  • When a website is without a sitemap

What Is Indexing in Search Engine?

The step of search engines working is indexing. Post crawling, search engines like google work on understanding the content and relevance of webpages.

The relevancy is examined by screaming textual content, codes like HTML Tags (Title, Description, Robots Tag, Canonical), Javascript, CSS, alt attributes, images, videos, pdf, etc.

As the indexing process kicks off, the Google search engine tries to figure out whether the content is a duplicate of another webpage in the Index database or canonical. Canonical can be the same webpage URL or a copy of another web page of the same website.

To select the canonical, the google search engine group the pages found on the internet’s index database with similar content. The most relevant webpage that adheres to the content is then selected. Among the other pages in the group are alternate versions that may be served differently depending on the context, such as mobile devices or a specific page in the group.

During the next stage, Google will serve the canonical page in search results and collect signals about it and its contents. Some signals include language, the country the content belongs to, the usability of the page, and so on.

Thus, the canonical page and its cluster may store in the search engine’s index.

How can you find web pages indexed?

Search Engine Result Page Featuring Indexed URL of a website

When you type (e.g., in the google search bar, you will get a search engine results page (SERP). It only features the URL of your website that is indexed. This methodology is known as an advanced search operator.

How to Check the Indexed page in Google Search Console

The next way is by accessing Google Search Console, a free tool by Google to inspect the technical behavior of the website. Under this tool, navigate towards the section coverage. Click on the valid option to find all the indexed web pages.

Best Practices for Indexing:

  • Always try to keep your webpage live. Never should it fall under the response code of 4xx or 5xx.
  • If you permanently move the webpage URL to a new one, provide with 301 redirect command.
  • Always build a new page with a reference from an existing or known page to the Google index. We call this internal linking.
  • Create quality and expertise content to get external links from quality websites, known as backlinks. It can increase the chances of indexing at higher rates.
  • Once you have completed creating a new web page, use Google Search Console to try manual indexing.
  • Under URL Inspection, you can paste the URL and push Google to discover the URL.
  • Post that, you will get a result stating the URL is not on Google. The next step is to click on Test Live URL.
  • Once test live is done, and if your web page passes the response code 200, you will get the command URL is available to Google.
  • Finally, you have to Request Indexing. Yet, Google takes its own time and decisions to index the page. Request Indexing doesn’t mean indexing the web page, as Google looks at various factors before indexing.
  • Always try to keep Robots Tag to index, and follow your web page if you look for indexing.

Understand the Role of Robots Meta Tag in Indexing:

The robots meta tag is used within the header of the HTML of your webpage. It can exclude or include search engines to index, pass, or hold the link juice. Here are the most common Robots tags used to command.

Index: This tells the search engines whether the page should be added to the search index post crawling. The search engine assumes that all pages will be indexed by default, so the “index” value is unnecessary.

Noindex: If you opt to use “noindex,” you’re communicating to crawlers that you want the page excluded from search results. 

If you are trying to remove thin pages (ex: user-generated profile pages) from Google’s index of your site but still want them visible to visitors, you might mark a page as “noindex.”

Follow: This robots tag allows the google search engines to follow all the links on the page and passes link juice or equity to the pages that are linked/referred. The “follow” robot tag is automatically applied to all pages by default.

Nofollow:  This robots tag disallows the search engines to follow any link inserted on a web page. It also stops from transferring the link juice or link equity to the other linked web pages.

In conjunction with noindex, nofollow is used to prevent the crawler from following links on a page and prevent it from being indexed.

Noarchive: This prevents search engine caches from storing the page. By default, all pages indexed by the engines will remain cached and accessible through the cached link in the search results. 

The noarchive tag can prevent searchers from seeing outdated pricing on your e-commerce site if your prices change frequently.

How to check the cached version of Google Bot?

Enter the URL in the search bar of Google; you will get search features, i.e., an organic result page.

Near the URL, you can see three dots. Once you press them, you will get a pop, as shown below.

Googlebot Cached Version of Web Pages

You can click on cached to check the version of the last crawling by search engines.

What can be the reasons behind web pages removed from Index Database?

  • When a webpage HTTP response code returned as 404 (page not found), 4xx, server errors (5xx)
  • Webpages with “Noindex” meta tags.
  • Low quality of content
  • Orphaned page
  • Backlinks from Spammy websites
  • Google penalizing as an act of link scheme

What is Search Engine Ranking?

Once the search engine completes crawling and indexing, the next function of the search engine is to find how to rank and where to rank in SERP.

Google has about 200+ core ranking factors or algorithms before it ranks or provides a position in the first 10 pages. The algorithms vary from search engines to search engines.

Since Google has a market share of 92.07%, this ranking section is focused on Google’s ranking system and algorithm.

No SEO expert across the globe knows what those 200+ ranking factors are, yet there is key factors the SEO team focus on to get a feature on the first page of google. They are,

  • Topical Authority
  • Relevance
  • Backlinks
  • On-Page Optimization
  • The freshness of the content
  • Page Experience

Topical Authority

Google looks at any website which holds authority over a topic. If Google crawls for any query, the website should contain 360 degrees of information on the subject as the topical authority. This has been one of the important Google ranking factors that many websites miss out.

As per Ahrefs, 96.55% of the content on the web gets zero organic traffic. The main reason is websites fail to build Topical Authority when you create a series of expertise content that covers all the information.

When a website contains expertise in a seed topic, it becomes trustworthy on the particular topic. So, Topical authority covers two factors of the E-E-A-T Algorithm.

Let’s look at how topical authority pushes your web pages higher in organic position than a web page with a high page rank.

Topical Authority - Differentiation

For the keyword best protein powder, the three web pages as per the above image are placed in the first three positions of the SERP 1st page.

In this, Healthline has a higher page rank than LiveScience and muscleblaze. Yet, these two websites have overcome Healthline only because of topical authority.

To build topical authority for any seed topic, be specific in answering all the queries that a user can ask. You can use the free tool Answer the Public to find out the questions.


Initially, google search engine relevancy was estimated by matching the keywords used in the web page to the query asked by users. Relevancy has been a predominant Google ranking factor. But, the measurement of relevancy has been updated.

Post the Google algorithm updates like HummingBird, and Rank Brain, user intent that matched the query got featured in search engine result page than a matched keyword.

After the BERT update in 2019, search engines matched both user queries and the relevancy of web pages with NLP (Natural Language Programming).

To help understand the relationship between people, places, and things, Google has invested in technologies such as Machine Learning (ML) and Artificial Intelligence (AI).

Even Google occasionally rewrites queries to provide more relevant results.

So, the relevancy of web pages should be focused on while practicing SEO.


There is a difference between backlinks and link building. Yet, both serve the same purpose in SEO, i.e., the authority of a web page. The quality of any web page is decided on the rate of natural backlinks it gets from relevant and high Page Rank websites.

Backlinks are one of the focused ranking factors of Google. It was confirmed in a live event by a Search quality senior strategist at Google, who stated that the two important factors for ranking are Content and link building.

Backlinks have been in the SEO practice since Google introduced Page Rank in 1997. Page Rank is the metric used by Google to estimate the authority and quality of web pages. The authority is calculated by the quality of links redirected to the web page.

Page rank of high authority page is divided equally with the number of links it refers. For example, page A which has a high authority of page rank 40, refers to 10 other web pages. So, each linked web page gets a page rank of 10. This process is known as link equity or link juice.

When referring domain of your website increases, the chances of keywords rankings and organic traffic increase. Yet, the quality of backlinks determines the ranking.

Factors for a Quality Backlinks:

  • High Authority (Page Rank)
  • Relevant niche
  • The referring domain should have robots tag as “follow.”
  • Relevant Anchor Text


On Page Optimization:

This involves optimizing the HTML tags (Title, Description, header), Alt Image, and URL with the focused keyword. It is one of the important parts of On-Page SEO, and it occupies the Google Core ranking system.

The title tag and Meta description should be under the limit of 60 and 150 characters each. These two tags should contain focus and related keywords, and the copy should attract high CTR (Click Through Rate).

The next important parameter is URL. It should be less than 75 characters and contain the keyword for ranking. The best SEO practice on URLs is that the slug should only have hyphens to separate phrases.

Then comes header tags optimization. H1, the most important header tag, builds the web page’s hierarchy. Google search engine looks at H1 tags to find the intent and relevancy of the webpage. H1 tags in the SERP feature have recently replaced the title tag.

The next factor is Alt Image. Search engines don’t understand the image; it only understands the Alt Image tag. So, optimize the image with the keyword relevant to the content on the image. Image SEO is another crucial part of SEO that can bring huge organic traffic to the website.

Freshness of the Content:

Accordingly, freshness is more important for some results than others, depending on the query.

When a user need a content with current update like “New Ferrari Car”, the website with the latest content or latest update will be ranked higher.

At the same time, the crawl budget increase, when you update your website with more content or update exiting content.

Page Experience of Web Pages:

Quite an intresting ranking factor is Page Experience for both mobile and desktop. This become a ranking factor, as Google always give priority to user experience.

This page experience has five core compenents,

  • Core Web Vitals
  • Website Security (HTTPS)
  • Mobile-Friendliness
  • Safe Browsing
  • Avoid Intrusive Interstitial.

Core Web Vitals:

In this Core Web Vital was on of the key component and a ranking factor as on June 2021, when it comes to website loading speed.

Core web vital looks for three parameters

The core web vital reports are live in Google Search Console for both Mobile and Desktop.

You should always focusing in passing the core web vitals. We have seen a great drop in keyword position and organic traffic when a webpage fails in CWV.

Mobile Friendliness:

Over 65% of all Google searches occur on mobile. Since 2015, after the mobilegeddon algorithm update, mobile-friendliness has been an important consideration. 

From 2019, Google search engine focused at Mobile-friendliness as one of the prime ranking factor. Now, Google look at Mobile-First Index. Google indices and ranks content across all devices mainly on the basis of the mobile version.

You can check out the mobile-friendliness of any web page with Mobile friendly Test Tool, a free tool by Google.


  • Google is the largest search engine, with a market share of 92.07%
  • Google search engine works on three processes. They are Crawling, Indexing, and Ranking.
  • Crawling is the process of discovering the URL and understanding the web page’s content.
  • Indexing is the process of analyzing the web page’s relevancy and checking with the search index database to find out if there is any copy of the same present in the database.
  • Post that, the search engine provides a canonical tag and index the new URL that you submit
  • Google ranking factors are 200+, yet the main factors are Topical authority, Backlinks, Freshness of Content, Relevancy of webpages, On-page Optimization, and Page Experience.
Picture of Ashkar Gomez

Ashkar Gomez

Ashkar Gomez is the Founder of 7 Eagles (a Growth Marketing & SEO Company). Ashkar started his career as a Sales Rep in 2013 and later shifted his career to SEO in 2014. He is one of the leading SEO experts in the industry with 8+ years of experience. He has worked on 200+ projects across 20+ industries in the United States, Canada, the United Kingdom, UAE, Australia, South Africa, and India. Besides SEO and Digital Marketing, he is passionate about Data Analytics, Personal Financial Planning, and Content Writing.

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