Search Engine Basics: Crawling, Indexing & Ranking


Search engines work as an answering machine would. Their main purpose is to explore, recognize, and arrange all of the content published on the internet. When a query is entered inside of a search bar, the engine digests the most relevant results for the given word or phrase.

There are trillions of pages out there on the Web, and yet, a user can get millions of useful results in a matter of one second. For your website to appear as the first-page search result, you need to understand what happens in that one second after you hit the Enter key. So…

How Does a Search Engine Work?

Lots of businesses are competing for online attention, and the number of websites is only getting higher. In that ocean of information, a search engine undertakes three main operations in order to create a selection for the user:

  • Crawling: Going after content, scouring the substance of each URL that pops up.
  • Indexing: Gathering found the content in an organized way, and saving that information for future searches. 
  • Ranking: Delivering parts of gathered content that answer the search query best – from most to least relevant. 

Robots, Crawlers, And/Or Spiders

Search engines have a huge helping team of robots, known as “crawlers” or “spiders”. Based on algorithmic processes, robots choose which sites to crawl. They are discovering new content by memorizing all website links they encounter during the crawling process and adding them to a list for future purposes. That content can be anything – a webpage, video, document, or an image, but in the form of a link.

Building An (Almost) Infinite Database

Once the crawling process is done, the search engine creates a colossal database of all words it encounters and places where they were found. The selection of content is being indexed, organized, and clarified by the algorithm. After it’s interpreted, search engines can measure the importance of information one website has in comparison with the other ones. 

Here’s a closer look at what indexing process organize:

  • Comprehensive data based on the type of content and topic relevance
  • A web of all the pages linked between each other
  • Anchor text of any links that may appear
  • Nature of the links – where are they located, are the ads or not, and much more

Result Ranking

Before you receive the closest match based on your search query, there is an algorithm determining how to rank web pages connected to your search. There are hundreds of ranking signals which judge the indexed content. By scoring the content, a search engine will present the most applicable result.

Relevance And Importance

When you decide to take good care of your SEO strategy, you’re mostly working on influencing the relevance and importance of your website content. And how does it differ?

  • Relevant content – matches the search intent, or what the person searching is trying to accomplish.
  • Important content – trustworthy information in form of a link, cited on other websites.

Content Evaluation

A crucial part of the ranking is understanding the information of crawled web pages. To do so, search engines create “semantic maps”, which help define the relationships between linked web pages on one website.

To do so, the codes of every crawled page are being analyzed. Differently put, search engines “make sense” of information it faces in the source code of the page. 

The two elements crawlers find very helpful in sense of content evaluation are:

  1. Web page’s metadata: title tags and meta descriptions based on the HTML code. 
  2. Alt attributes for images: textual, code-like descriptions of images that appear on a web page, maintained by the website owner. 

Let Them Know How To Index Your Site

Meta tags or meta directives are textual instructions you can give to engines in case you want some information on your website to remain unseen.

The most used ones are robots meta tags, which are found in the <head> of the HTML. They can exclude specific or even all search engines. 

search engine

Is Your Content Visible?

Your goal within an SEO strategy is to position your website on the first few SERPs. Having your web pages indexed well will improve the crawling process and make your website more visible to the search engine. 

Although, your content may appear invisible. Here are some reasons why:

  • Your site is still fresh and new and hasn’t been crawled yet (it can take up to several weeks for this process to be completed).
  • You don’t have any external content linked to your website. 
  • There are blocks in the form of crawler directives on your website that are preventing your content from being crawled.
  • Navigation of your site is too complicated for a robot to crawl it well.
  • You’ve been penalized by Google for using spammy (black hat SEO) tactics.

Can Spiders Find All Important Content On Your Website?

Sometimes, the crawling process can leave out some important stuff from your website. A great question to keep in mind is: Can spiders crawl through my website, not just to it?

The main reasons why your content may be left out in the crawling process are:

  • Your content is hidden behind login forms, answer surveys or fill out forms. These are blocking crawlers from seeing the information behind them.
  • Your content can be found only through a search form. But the problem is, search engines cannot go through the content that’s not well-placed and seen.
  • The text you want to be indexed is in a non-text form.
  • Your website has pages that are not linked to any other ones in your navigation system, and thus remain invisible.
  • Content on your website is not organized and labeled correctly, it’s not intuitive and as such remain hard to go through.


A search engine is always looking for one thing – to provide useful answers to a given search query in a format that is most helpful. As you get your results at the speed of light, you may think this process is like magic. But, as you can see, there is a lot more to understand in order to appear as a perfect answer to a searcher online. 

By knowing these basic principles of crawling, indexing, and ranking, you will be able to target your audiences correctly and therefore become that one solution or answer someone is looking for online.

Still having trouble understanding this? Don’t worry, we got you! At DSO, we can help you develop an amazing SEO strategy that will help you rank better and shoot your website up to the first page of Google!