The Basics of How Search Engine Indexing Works (2023)

Search Engine Optimization (SEO) is an essential ways to boost your website’s visibility and attract more organic traffic. However, it’s a complex strategy that relies on understanding algorithms and leveraging a wide variety of ranking factors. If you’re looking to become an SEO expert, you’ll need to understand search engine indexing.

In this post, we’ll explain how search engines index websites and how you can boost your rankings. We’ll also answer some frequently asked questions about this SEO concept. Let’s get started!

What Is Search Engine Indexing?

Search engine indexing refers to the process where a search engine (such as Google) organizes and stores online content in a central database (its index). The search engine can then analyze and understand the content, and serve it to readers in ranked lists on its Search Engine Results Pages (SERPs).

Before indexing a website, a search engine uses “crawlers” to investigate links and content. Then, the search engine takes the crawled content and organizes it in its database:

The Basics of How Search Engine Indexing Works (1)

Image source: Seobility – License: CC BY-SA 4.0

We’ll look closer at how this process works in the next section. For now, it can help to think of indexing as an online filing system for website posts and pages, videos, images, and other content. When it comes to Google, this system is an enormous database known as the Google index.

How Does a Search Engine Index a Site?

Search engines like Google use “crawlers” to explore online content and categorize it. These crawlers are software bots that follow links, scan webpages, and gain as much data about a website as possible. Then, they deliver the information to the search engine’s servers to be indexed:

The Basics of How Search Engine Indexing Works (2)

(Video) How Google searches one document among Billions of documents quickly?

Image source: Seobility – License: CC BY-SA 4.0

Every time content is published or updated, search engines crawl and index it to add its information to their databases. This process can happen automatically, but you can speed it up by submitting sitemaps to search engines. These documents outline your website’s infrastructure, including links, to help search engines crawl and understand your content more effectively.

Search engine crawlers operate on a “crawl budget.” This budget limits how many pages the bots will crawl and index on your website within a set period. (They do come back, however.)

Crawlers compile information on essential data such as keywords, publish dates, images, and video files. Search engines also analyze the relationship between different pages and websites by following and indexing internal links and external URLs.

Note that search engine crawlers won’t follow all of the URLs on a website. They will automatically crawl dofollow links, ignoring their nofollow equivalents. Therefore, you’ll want to focus on dofollow links in your link-building efforts. These are URLs from external sites that point to your content.

If external links come from high-quality sources, they’ll pass along their “link juice” when crawlers follow them from another site to yours. As such, these URLs can boost your rankings in the SERPs:

The Basics of How Search Engine Indexing Works (3)

Image source: Seobility – License: CC BY-SA 4.0

Furthermore, keep in mind that some content isn’t crawlable by search engines. If your pages are hidden behind login forms, passwords, or you have text embedded in your images, search engines won’t be able to access and index that content. (You can use alt text to have these images appear in searches on their own, however.)

(Video) SEO For Beginners: Crawling, Indexing and Ranking

4 Tools for Search Engine Indexing

You can use several tools to guide how Google and other search engines crawl and index your content. Let’s look at a few of the most helpful options!

1. Sitemaps

Keep in mind that there are two kinds of sitemaps: XML and HTML. It can be easy to confuse these two concepts since they’re both types of sitemaps that end in -ML, but they serve different purposes.

HTML sitemaps are user-friendly files that list all the content on your website. For example, you’ll typically find one of these sitemaps in a site’s footer. Scroll all the way down on, and you will find this, an HTML sitemap:

The Basics of How Search Engine Indexing Works (4)

This sitemap enables visitors to navigate your website easily. It acts as a general directory, and it can positively influence your SEO and provide a solid user-experience (UX).

In contrast, an XML sitemap contains a list of all the essential pages on your website. You submit this document to search engines so they can crawl and index your content more effectively:

The Basics of How Search Engine Indexing Works (5)

Keep in mind that we’ll be referring to XML documents when we talk about sitemaps in this article. We also recommend checking out our guide to creating an XML sitemap, so you have the document ready for different search engines.

2. Google Search Console

If you’d like to focus your SEO efforts on Google, the Google Search Console is an essential tool to master:

The Basics of How Search Engine Indexing Works (6)

(Video) What is indexing? How do search engines like Google and Bing index your site? - Indexing Course

In the console, you can access an Index Coverage report, which tells you which pages have been indexed by Google and highlights any issues during the process. Here you can analyze problem URLs and troubleshoot them to make them “indexable”.

Additionally, you can submit your XML sitemap to Google Search Console. This document acts as a “roadmap,” and helps Google index your content more effectively. On top of that, you can ask Google to recrawl certain URLs and parts of your site so that updated topics are always available to your audience without waiting on Google’s crawlers to make their way back to your site.

3. Alternative Search Engine Consoles

Although Google is the most popular search engine, it isn’t the only option. Limiting yourself to Google can close off your site to traffic from alternative sources such as Bing:

The Basics of How Search Engine Indexing Works (7)

We recommend checking out our guides on submitting XML sitemaps to Bing Webmaster Tools and Yandex Webmaster Tools. Unfortunately, other search engines, including Yahoo and DuckDuckGo, don’t enable you to submit sitemaps.

Keep in mind that each of these consoles offers unique tools for monitoring your site’s indexing and rankings in the SERPs. Therefore, we recommend trying them out if you want to expand your SEO strategy.

4. Robots.txt

We’ve already covered how you can use a sitemap to tell search engines to index specific pages on your website. Additionally, you can exclude certain content by using arobots.txt file.

Arobots.txtfile includes indexation information about your site. It’s stored within your root directory and has two lines: auser-agent line that specifies a search engine crawler, and a disallow directive that blocks particular files.

For example, a robots.txt file might look something like this:

User-agent: *Disallow: /example_page/Disallow: /example_page_2/

In this example, the *covers all search engine crawlers. Then, the disallow lines specify particular files or URL paths.

(Video) Crawling, Indexing, and Ranking | Lesson 2/31 | SEMrush Academy

You simply need to create a simple text file and name it robots.txt. Then, add your disallow data and upload the file to your root directory with a File Transfer Protocol (FTP) client.


So far, we’ve covered the basics of search engine indexing. If you still have questions about this SEO concept, we’ll answer them here! (And if you still have one, let us know in the comments so we can answer it there!)

How Can I Get Indexed Better by Search Engines?

You can get indexed better by search engines by creating sitemaps, auditing them for crawling errors, and submitting them to multiple search engines. Additionally, you should consider optimizing your content for mobile devices and reducing your loading times to speed up crawling and indexing.

Frequently updating your content can also alert search engines to crawl and index your “new” pages. Finally, we recommend preventing search engines from crawling duplicate content by using arobots.txt file or deleting it.

Do I Have to Request Search Engines to Crawl My Site?

Search engines will crawl new publicly-available content on the internet, but this process can take weeks or months. Therefore, you might prefer to speed things up by submitting a sitemap to the search engines of your choice.

Do I Have to Alert Search Engines if I Publish New Content?

We recommend updating your sitemap when you publish new content. This approach ensures that your posts will be crawled and indexed more quickly. We recommend using a plugin such as Yoast SEO to generate sitemaps easily.

Is My Content Ever Removed From Google or Other Search Engines?

Google might remove a post or page from its index if the content violates its terms of service. This means the content breaks privacy, defamation, copyright, or other laws in many cases. Google also removes personal data from its index, such as identifiable financial or medical information. Finally, Google may penalize pages that use black hat SEO techniques.

How Can I Get My Content Re-Indexed if It’s Been Removed?

You can ask Google to re-index your content by modifying it to meet the search engine’s Webmaster quality guidelines. Then, you can submit a reconsideration request and wait to see Google’s response.

How Can I Prevent Search Engines From Indexing Certain Pages?

You can prevent search engines from indexing certain pages by adding anoindex metatag to the page’s <head> section. Alternatively, if your content is a media file, you can add it to arobots.txt file. Finally, Google Webmaster Tools enables you to hide a page using the Remove URLs tool.


SEO is a broad field that covers everything from search engine algorithms to off-page optimization techniques. If you’re new to the topic, you might be feeling overwhelmed by all the information. Fortunately, indexing is one of the easier concepts to grasp.

(Video) The Internet: How Search Works

Search engine indexing is an essential process that organizes your website’s content into a central database. Search engine crawlers analyze your site’s content and architecture to categorize it. Then they can rank your pages in their results pages for specific search terms.

Do you have any other questions about search engine indexing? Let us know in the comments section below!

Featured image via Sammby /


How does indexing work as a search engine? ›

Indexing is the process by which search engines organize information before a search to enable super-fast responses to queries. Searching through individual pages for keywords and topics would be a very slow process for search engines to identify relevant information.

How does a search engine works step by step? ›

Search engines work by simply crawling billions of pages using the web crawlers they have developed. These are commonly referred to as search engine spiders or bots. A search engines spider then navigates the web by following links on a new web page it discovers to find new pages and so forth.

How does a search engine use an index and algorithm? ›

When a search query is entered into a search engine by a user, all of the pages which are deemed to be relevant are identified from the index and an algorithm is used to hierarchically rank the relevant pages into a set of results. The algorithms used to rank the most relevant results differ for each search engine.

What are the 3 basic tasks of a search engine? ›

The three main functions of a search engine are collecting information about webpages, categorizing those webpages, and creating an algorithm that makes it easy for people to find relevant web pages. Google is by far the most well-known search engine.

What is indexing and how it works? ›

Indexing is the way to get an unordered table into an order that will maximize the query's efficiency while searching. When a table is unindexed, the order of the rows will likely not be discernible by the query as optimized in any way, and your query will therefore have to search through the rows linearly.

What is the process of indexing? ›

Indexing proceeds at four stages namely content specification, tokenization of documents, processing of document terms, and index building. The index can be stored in the form of different data structures namely direct index, document index, lexicon and inverted index.

What are the basics of search engine? ›

3-steps of Search Engines: Crawling, Indexing, and Ranking.
  • Crawling - This is the process that search engines use to discover new content. ...
  • Indexing - The search engines maintain a copy of the content of all web pages they have visited. ...
  • Ranking - This is the area of search engines that SEO is most concerned with.

What are the four basic steps of search engine marketing? ›

4 Elements of SEM

SEM is comprised of four main elements: search engine optimization, paid search or PPC advertising, and website and landing page optimization. Collectively, these four elements work to create a sustainable strategy for getting found in search quickly and in the long term in a cost-effective way.

What are the five elements of a search engine? ›

Dialog: the five elements of SERP (search engine results page) The five elements of a search engine are: documents, index, user query, ranking model and results page (SERP).

How many types of indexing methods are used by search engines? ›

Google Has Two Kinds Of Crawling

Indexing by Google begins with crawling, which has two kinds. The first kind of crawling is Discovery, where Google discovers new webpages to add to the index. The second kind of crawling is Refresh, where Google finds changes in webpages that are already indexed.

What is the main purpose of an index? ›

An index is a list of all the names, subjects and ideas in a piece of written work, designed to help readers quickly find where they are discussed in the text. Usually found at the end of the text, an index doesn't just list the content (that's what a table of contents is for), it analyses it.

What does Google use for indexing? ›

We use a huge set of computers to crawl billions of pages on the web. The program that does the fetching is called Googlebot (also known as a robot, bot, or spider). Googlebot uses an algorithmic process to determine which sites to crawl, how often, and how many pages to fetch from each site.

What are the 4 types of search engines? ›

4 types of search engines
  • Mainstream search engines. Mainstream search engines like Google, Bing, and Yahoo! are all free to use and supported by online advertising. ...
  • Private search engines. ...
  • Vertical search engines. ...
  • Computational search engines.
6 Nov 2021

What are the 2 main functions of a search engine? ›

Web search tools have two noteworthy capacities: crawling and indexing, both concepts are a part of search engine process where the users are provided with the list of well-ranked websites on Google.

What is indexing in simple words? ›

Indexing, broadly, refers to the use of some benchmark indicator or measure as a reference or yardstick. In finance and economics, indexing is used as a statistical measure for tracking economic data such as inflation, unemployment, gross domestic product (GDP) growth, productivity, and market returns.

What are the steps for indexing a file? ›

Indexing steps
  1. Crawl all pages of the seedlist and persist them to disk.
  2. Extract the file content and persist it to disk.
  3. Crawl a seedlist page from disk.
  4. Index the seedlist entries into Lucene documents.
  5. Write the documents to the Lucene index.
  6. Repeat until all the persisted seedlist pages have been crawled.

What is indexing and types of indexing? ›

Indexing is a small table which is consist of two columns. Two main types of indexing methods are 1)Primary Indexing 2) Secondary Indexing. Primary Index is an ordered file which is fixed length size with two fields. The primary Indexing is also further divided into two types 1)Dense Index 2)Sparse Index.

What are the three types of indexing? ›

Types of indexes
  • Unique indexes enforce the constraint of uniqueness in your index keys.
  • Bidirectional indexes allow for scans in both the forward and reverse directions.
  • Clustered indexes can help improve the performance of queries that traverse the table in key order.

What are the basic steps of indexing pipeline? ›

In the following diagram, the indexing pipeline stages over which you can exercise control have a bright orange background. This article provides an overview of each of those stages.
About the Indexing Process
  • Crawling.
  • Applying Extensions.
  • Optical Character Recognition.
  • Processing.
  • Mapping.
  • Indexing.
  • What's Next?

How does SEO work in simple words? ›

Well, SEO stands for 'Search Engine Optimization', which is the process of getting traffic from free, organic, editorial, or natural search results in search engines. It aims to improve your website's position in search results pages. Remember, the higher the website is listed, the more people will see it.

What are the six basic search techniques? ›

General search techniques that can be used in most databases and search engines are briefly described below.
  • Subject headings. In various databases, subject headings are assigned to publications. ...
  • Fillers. ...
  • Combining search terms. ...
  • AND. ...
  • Nesting terms. ...
  • Phrase searching. ...
  • Proximity operators (NEAR, NEXT, ADJ) ...
  • Truncating words.

What are the 3 parts of SEO? ›

The three main components of SEO are: Technical SEO. On-page SEO (or Content SEO) Off-page SEO (or Links)

What are the tools of indexing? ›

Some tools that allow for embedded indexing include FrameMaker, Microsoft Word, Adobe InDesign (or the older PageMaker), Madcap Flare, and Quark Xpress. Markup languages that allow for embedding indexing include SGML, HTML, XML and TeX/LaTeX.

What is the most common form of indexing? ›

B-tree-indexing is one of the most popular and commonly used indexing techniques. B-tree is a type of tree data structure that contains 2 things namely: Index Key and its corresponding disk address. Index Key refers to a certain disk address and that disk further contains rows or tuples of data.

What are the types of indexing? ›

Types of indexing
  • Bibliographic and database indexing.
  • Genealogical indexing.
  • Geographical indexing.
  • Book indexing.
  • Legal indexing.
  • Periodical and newspaper indexing.
  • Pictorial indexing.
  • Subject gateways.

What is index example? ›

Indices can be broad-based or track the performance of specific sectors/stocks etc. For example, the Nifty is a broad-based index which tracks the performance of the top 50 stocks listed on the National Stock Exchange (NSE).

Why getting indexed by Google is so difficult? ›

If your page doesn't provide unique, valuable content that Google wants to show to users, you will have a hard time getting it indexed (and shouldn't be surprised). Google may recognize some of your pages as duplicate content, even if you didn't mean for that to happen.

How does Google build its index? ›

Most of our Search index is built through the work of software known as crawlers. These automatically visit publicly accessible webpages and follow links on those pages, much like you would if you were browsing content on the web.

What is the difference between a browser and a search engine? ›

Let's make it clear: A browser is a piece of software that retrieves and displays web pages; a search engine is a website that helps people find web pages from other websites. The confusion arises because, the first time someone launches a browser, the browser displays a search engine's homepage.

What is a search engine give at least 5 examples? ›

A search engine is a platform on which a user can search the internet content. Google, Yahoo, Bing, Baidu, and DuckDuckGo are popular search engines. Google is one of the most used search engines worldwide that is used with the Chrome browser. So, almost everyone is familiar with it.

What is indexing and ranking? ›

Indexing: is the gathering of contents found during the crawling process. If a page is on this list, it means that the search engine indexed it, and it can appear among the search results for the related queries. Ranking: is the order in which the indexed results appear on the result page (SERP).

What is a search engine algorithm? ›

A search engine algorithm is a collection of formulas that determines the quality and relevance of a particular ad or web page to the user's query. Google reportedly changes its algorithm hundreds of times each year. The good news: only major changes (or updates) have the power to affect SEM campaigns significantly.

What is crawling and indexing? ›

Crawling is the discovery of pages and links that lead to more pages. Indexing is storing, analyzing, and organizing the content and connections between pages. There are parts of indexing that help inform how a search engine crawls.

What is known as the number 1 search engine in the world? ›

1. Google. With over 86% of the search market share, one hardly needs to introduce readers to Google. However, it clearly needs to head up any list of search engines.

How does indexing makes search faster? ›

Indexing makes columns faster to query by creating pointers to where data is stored within a database. Imagine you want to find a piece of information that is within a large database. To get this information out of the database the computer will look through every row until it finds it.

What is the purpose of indexing? ›

Indexing, broadly, refers to the use of some benchmark indicator or measure as a reference or yardstick. In finance and economics, indexing is used as a statistical measure for tracking economic data such as inflation, unemployment, gross domestic product (GDP) growth, productivity, and market returns.

What are types of indexing? ›

Types of indexing
  • Bibliographic and database indexing.
  • Genealogical indexing.
  • Geographical indexing.
  • Book indexing.
  • Legal indexing.
  • Periodical and newspaper indexing.
  • Pictorial indexing.
  • Subject gateways.

What factors affect the efficiency of indexing? ›

The speed of indexing will depend on the power of the hardware involved. Indexing speed depends on CPU and I/O capacity. Given sufficient I/O capacity to read in the original data and write out index entries, then CPU will be the limiting factor.

How many methods are indexing? ›

There are primarily three methods of indexing: Clustered Indexing. Non-Clustered or Secondary Indexing. Multilevel Indexing.


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