How Search Engines Work: Crawling, Indexing, and Ranking

How Search Engines Work

To appear on search results, it is important that your website is accessible to search engines. Without visibility, your site will not be found on the SERP. Search engines primarily work in three ways:

  1. Crawl: Search through the internet for valid content.
  2. Index: Organize and save contents discovered when crawling.
  3. Rank: Provide the content to online users in an order, from the most useful to least useful.

Search Engine Crawling

Crawling is a search process where search engines disperse robots to locate valid content. This content can be a website, video, images, PDF and so on. Contents are found by links.

Search Engine Index

Search engines organize and save contents they discover in an index. The index is a big database containing all the contents found to be good enough to meet online users needs.

Search Engine Ranking

When an online user searches for information online, search engines look through the index for useful information and then arranges these contents in a way that would hopefully be able to provide the needed information. The ordering of web content on the search result page is called ranking. In order words, the more relevant content is, the higher it gets ranked on SERP.

You can make your web content easily found by online users, but this can only be achieved if crawlers can access it and save it to its index. Without this, your content will be invisible online. Here you will get information on how to make your content visible to search engines.

Can your site be found on search engines?

As mentioned earlier, before a site can be found, it needs to be crawled and indexed. As a website owner, it is advisable that you begin by checking out the number of webpages you have in the index. This will give you insights on whether Google is finding the pages you require it to.

You can check your indexed pages by typing “” into your Google search bar. This will provide the index result Google has for the specific site. Although the number of results provided by Google might not be exact, it can provide you with a good idea of the indexed pages on your site. To get precise results, use and follow Index Coverage report on the Google Search Console.

If your site is not accessible on any search result, it could be because:

  1. You newly opened your site; hence it has not been crawled.
  2. The navigation of your site makes it difficult for robots to properly crawl it.
  3. There are no links to your site from external websites.
  4. There are basic codes on your site which blocks search engine crawlers.
  5. Google penalized your site for spam.

Direct search engines to crawl your website

If you used “” or Google Search Console and discovered some of your essential pages are not included on the indexed or the unimportant pages have been indexed instead, then you can influence the Googlebot to crawl your web site the way you want. This can provide you with a control on which of your pages gets indexed.

To prevent Google from finding some pages, you can make use of robots.txt.

Robots.txt. are files situated in the directory of websites and selects the areas of your website which should or should not be crawled by search engines. This is how it works: If Googlebot is unable to locate a robots.txt file of a website, it goes ahead to crawl the website. If a robots.txt file is found by Googlebot for a site, it will most likely follow the suggestions given by the file and crawl the site. If an error is encountered by Googlebot when trying to crawl a site, then the site won’t be crawled.

How to ensure crawlers find your important content

Now that you know how to keep crawlers from finding unwanted contents, it is time to understand how you can help Googlebot locate the important pages.

Sometimes, search engines can locate some pages of your website by crawling and be unable to find other pages due to one reason or the other. You need to ensure that the web content you want to be indexed can be accessed by search engines. Hence it is necessary for the bots not to only crawl to your website but also through it.

–        If your content is shielded behind login forms, e.g., ‘logins, filling forms, answering a survey, etc.’ then search engines will not be able to access those pages. Crawlers cannot log into pages.

–        If you rely on search forms, search engines will be unable to access your page because robots cannot make use of search forms.

–        If your text is put within non-text content such as videos, images, and GIFs, then it will be harder for search engines to access your webpage.

After ensuring your website can be crawled, the next step is to make sure it is indexed properly.

How are your pages found and stores on search engines index

The fact that your site can be crawled is no assurance that it will be saved in a search engine’s index. An index is where your site’s found pages will be saved. You can see how Googlebot crawlers view your page through the cached view of your page which will show a snapshot of the previous time it was crawled by Google. Google caches and crawls pages at various frequencies. You can check your page’s cached version by clicking on the drop-down arrow close to the URL on the search engine result page and selecting cached.

Do pages get excluded from the index?

Yes, pages get removed from the index. This could be because:

–        The URL is showing a server or not found error. Sometimes this happens accidentally when a page is moved, and it could also be intentional if the page is deleted.

–        The URL has a no-index meta tag attached. Often times this tag is put by site owners to tell search engines to remove the site from its index.

–        The URL is being penalised by the search engine for violating its guidelines.

–        The URL requires a password before the page can be accessed by visitors.

You can guide URLs on how to index your website with meta tags or meta directives. These are instructions given to search engines on how you want your website treated. These instructions are given through robots meta tags in your HTML page.

How search engines rank URLs

Search engines determine the relevance of content through algorithms. These algorithms retrieve and arrange information in meaningful ways. The algorithms used by search engines are constantly improved to ensure quality search results are always provided to online users.

To be ranked highly on SERPs, you need to provide relevant answers to a searchers question in an organised format. Once upon a time search engines could not fully comprehend our language, so it was possible to trick them by frequently repeating a keyword to make the content appear relevant and increase web ranking. Now though, algorithms review content to ensure it really is relevant before it can be ranked highly on SERPs.

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