How Search Engines Work: Crawling, Indexing, Ranking, & More

If you've ever wondered how search engines work, you've come to the right place. 

In this beginner's guide, you'll learn everything from crawling and indexing to ranking and penalties. 

Search engines act as librarians, curating and organising the vast amount of content on the internet for billions of users globally.

By understanding how search engines work, you can optimise your website to increase its visibility and attract more visitors. 

Troubleshooting tips will also be provided to help you overcome any challenges you may face. So let's dive in and explore the fascinating world of search engines.

How to Use This Guide on How Search Engines Work

This guide provides a comprehensive overview of how search engines work, as well as in-depth analysis of crawling, indexing, ranking, and penalties. To get started, simply select the section that interests you the most from the table of contents below:

• Overview - This section provides a quick summary of how search engines work.
  
  
  

• Crawling - Learn about how search engines discover new pages on the internet.
  
  
  

• Indexing - Discover how search engines organise and store the information they find.
  
  
  

• Ranking - Find out how search engines determine which pages to show first in search results.
  
  
  

• Penalties - Learn about the consequences of violating search engine guidelines.
  
  
  

Use this guide to gain a better understanding of how search engines work and how you can optimize your website to improve your search engine rankings.

How Search Engines Work?

Search engines use web crawlers to discover online content. The content is then analysed and stored in the search engine's index through indexing. When a user searches for something, the search engine ranks the most relevant content based on the user's search. This task is accomplished through processing programs, which act as the librarian of the internet. The market share of search engines varies depending on the language and region.

Crawling

Overview

Crawling is a crucial process in search engines that involves web crawlers or spiders scouring the internet to discover eligible content, including text, images, and videos. The process can also include previously crawled content. Crawling is similar to a librarian researching resources for their library. Without crawling, search engines cannot function, and the foundation of a search engine's index is incomplete.

The crawling process works by fetching existing content from the search engine's index and discovering new content. Given that crawling is expensive, search engines optimise crawling with an algorithm that determines which sites to crawl, how often to crawl them, and how many pages to crawl per site.

Optimisation

Webmasters can optimise crawling by implementing the following techniques:

• Create a robots.txt file: This file is like a gatekeeper that directs web crawlers to the content that should be indexed and the content that should remain out of search results, such as paid landing pages.
  
  
  

• Build an XML sitemap: This sitemap is like a city map that provides spiders with a complete list of your website content. Upload it to Google Search Console or Bing Webmaster Tools to provide these search engines' crawlers with a roadmap for visiting your site.
  
  
  

• Optimise internal linking: Internal links are like the roadways in a city that make travelling through town possible. Add three to five internal backlinks to each piece to help crawlers navigate your site and discover new content.
  
  
  

• Add canonical tags: These tags are like road signs that tell spiders where a URL and its content live. They also signal to web crawlers that you want this specific URL (listed as the canonical tag) indexed, which is essential for more complex site setups.
  
  
  

• Publish regularly: New or newly updated content signals to users and search engines that your website is active. When you publish regularly, say weekly or monthly, you can improve how often web crawlers visit your site.
  
  
  

Troubleshooting

If you're experiencing crawling errors, try the following troubleshooting steps:

• Audit your robots.txt file: When a robots.txt file disallows web crawlers, crawlers cannot crawl those site sections. Verify your robots.txt file settings with a third-party validator like Google's Robots Testing Tool, which allows you to enter a URL and view its crawl settings.
  
  
  

• Fix HTTP network errors: Different HTTP network errors, such as 404s and 301s, can cause crawling issues. Investigate these issues with a free tool like Screaming Frog or Google Search Console's Pages report, which highlights HTTP errors.
  
  
  

• Resolve server errors: Network issues, such as firewall settings, traffic spikes, or hosting issues, can also prevent spiders from reaching a website. Troubleshoot these errors by checking your settings, traffic issues, and hosting plan.
  
  
  

Indexing

Overview

Indexing is an essential process in search engines where crawled content is analysed, processed, and stored in the search engine's index. However, not all content is indexed, as low-quality, duplicate, or noindex content is excluded to maintain quality standards. Indexing is like a librarian organising their library, where search engines choose which content to admit into their database based on eligibility and quality standards.

Indexing is crucial because it builds a search engine's library with helpful content, and quality is critical to search engine results. Search engines analyse the content collected by crawlers and evaluate the content's canonical URL, title tag, images, videos, language, usability, and other elements to determine its eligibility for indexing.

Optimisation

To optimise your website for indexing, you can produce high-quality content that solves problems and demonstrates value to search engines. Adding meta tags, like title tags and meta descriptions, can help search engines better understand your URL's purpose. Use header tags, like H1, H2s, and H3s, to organise your content and help search engines understand its topic coverage.

Including multimedia, such as screenshots, graphics, stock photos, or videos, can help users and search engines better understand your topic. For images, add alt text so search engines can "read" the image. Building a user-friendly website that focuses on usability, like through a responsive design, and accessibility, like through high contrast text and background colours, can also help optimise your website for indexing.

It is also recommended to carry over some crawling optimizations, like including a canonical tag.

Troubleshooting

If you experience indexing issues, several troubleshooting ideas can help you resolve the problem. Checking for duplicate content using Google Search Console, Screaming Frog, and other SEO software can help you spot duplicate or near-duplicate content. You can resolve duplicate content by setting canonical tags, merging URLs through a 301 redirect, or rewriting content.

Analysing content quality using a resource like Google's helpful content guide can help you assess your content's quality. In this guide, you'll find a questionnaire that pushes you to evaluate a URL's originality, expertise, and value compared to other content on the web.

Testing content usability with Chrome Dev Tools, Google's Mobile-Friendly Test, or Google Search Console can help you test a URL's usability, accessibility, and speed on different devices, from desktops and laptops to tablets and smartphones. Crawling-based troubleshooting steps, like checking your sitemap and robots.txt file, also work here.

Ranking

Overview

Ranking is the process of generating search results in response to a user query. Search engines use complex algorithms that consider hundreds of factors to create personalised, relevant, and user-friendly results. The importance of ranking lies in the fact that it differentiates a search engine from its competitors. When a search engine can deliver more relevant and helpful results than a competitor, users are more likely to use and recommend that search engine.

Ranking happens in milliseconds and starts when a user enters a search query. Search engines respond by browsing their index. They look for the most relevant and high-quality content based on user and content factors, such as the user’s device and the content’s title tag, and then generate results.

Optimisation

To optimise your site for search engines, you can follow best practices of search engine optimization (SEO). These include:

• Targeting specific search queries: Including relevant search queries in your content, such as in your title tag, header tags, and written content, can help search engines gauge your content’s relevancy. Practising keyword research can help you discover the most relevant queries to target.
  
  
  

• Optimising for geographic areas: A user’s location also influences content relevancy. For localised searches, like “los angeles restaurants,” content focused on that topic and location will likely rank higher in search results. If this scenario applies to your site, target location-based queries.
  
  
  

• Writing for search intent: Use the content ranking for your targeted search queries to find ways to improve your content. For example, answering additional questions or restructuring content based on a user’s most important to least important needs can help create a user-focused URL.
  
  
  

• Reviewing search ranking factors: Search engines don’t publish their ranking factors, but they have confirmed several, like HTTPS, page speed, and content helpfulness, which you can use to optimise your content.
  
  
  

Crawling and indexing optimizations are also critical for SEO. You should check and optimize your robots.txt file, sitemap, canonical tags, internal linking, meta tags, header tags, multimedia, content quality, and website usability. Our free SEO checklist can help you learn more about these optimizations in-depth.

Troubleshooting

If you’re experiencing issues with ranking, you can try these troubleshooting tips:

• Evaluating search intent: Search intent (or what users seek when searching for something) can change over time. Compare your targeted query’s search results against your content and see if the intent has changed and made your content irrelevant.
  
  
  

• Investigating keyword metrics: Like search intent, search volume can also change. A free tool like Google Trends can help you see a keyword’s popularity over time and its potential impact on search results. A spike in popularity, for instance, can result in more competitive search results.
  
  
  

Crawling and indexing troubleshooting steps like auditing your robots.txt file, fixing your HTTP network errors, resolving your server errors, checking your site for duplicate content, analysing your content’s quality, and testing your content’s usability can also be relevant.

With the above troubleshooting tips, you can discover potential ranking issues and take action to improve your website’s visibility and relevance in search results.

Penalties

Overview

Penalties are a way for search engines to demote or remove a website from their index. This is done when search engines detect indexed content that violates their spam policies or attempts to manipulate their index. Penalties are similar to a librarian removing a book from their library. They help search engines maintain a reputable index and serve relevant and high-quality search results. Without penalties, search engines would waste resources on crawling, indexing, and serving sites that manipulate their index or violate their policies.

Search engines use automated systems, specialised team members, and search quality user reports to detect content that violates their policies. If detected, search engines will issue a manual action against the site and/or serve the affected content lower or not at all in results.

Optimisation

Webmasters can optimise their websites to prevent penalties by avoiding the following:

• Cloaking: Presenting different content to search engines than to users.

• Hidden text: Adding text that search engines can see (but users can’t), like by having white text on a white background.

• Keyword stuffing: Inserting keywords to the point of affecting readability.

• Link spam: Purchasing external backlinks to your site.

To prevent penalties, build links to your website naturally by producing helpful content that speaks to the reader’s unique pain points and needs. Review search engine's full spam policies to learn what not to do when working with them.

Troubleshooting

If you’re experiencing issues with penalties, check out these troubleshooting tips:

• For confirmed penalties: Review the penalty’s provided documentation to understand why the penalty happened and how to fix it. If you receive a Google penalty, view Google Search Console (and its Manual Actions report) to begin the resolution process.

• For unconfirmed penalties: Evaluate your content with the earlier troubleshooting steps for indexing and ranking. Look for common causes of unconfirmed penalties, like keyword stuffing or purchased backlinks.

In extreme cases, your website can get banned from a search engine’s index, which you can’t fix. If you’re unfamiliar with troubleshooting and resolving penalties, consider partnering with a reputable SEO service provider that specialises in them.

Learn More About How Search Engines Work

To improve your website's ranking on search engines, it's important to understand how they work. Search engines use complex algorithms to crawl, index, and rank web pages based on various factors, including relevance, authority, and user experience. Here are some key things to keep in mind:

• Search engines crawl the web to find new pages and content

• Pages are indexed based on their relevance and authority

• Ranking factors include keywords, backlinks, and user engagement

• User experience is becoming increasingly important for ranking

If you're new to SEO, consider reaching out to a professional SEO Consultant team for guidance on how to optimise your site for search engines.