What Is a Search Index?

Thanks to search indexes, search engine results take mere seconds to appear. But what is a search index?

By Lauryn Chamberlain

Jun 8, 2022

7 min

When you do a simple internet search, no matter what you're looking for, you receive results instantaneously (or as fast as your internet connection allows.) With millions of websites out there, how does this happen so fast? You'd think that since the search engines need to go through those websites in order to produce the results, the process would take longer.

Well, thanks to search indexes, getting relevant Google results takes a matter of seconds, not minutes. But how do search indexes work?

A Search Index Works Like a Book Index

The best way to describe a search index is by comparing it to a book index. If you wanted to find something in a large history book, rather than go through the entire thing page by page, you'd turn to the index and look for the subject or person that you want to learn about. This saves time and gives you an easy way to find exactly what you're looking for.

A search index is very similar. Only, instead of providing you with a list of book topics and subjects, it gives search engines a list of keywords that are discussed on the site. While there are no page numbers, as there would be in a book index, there are web pages, or URLs, instead.

These direct the search engines to the correct part of the site, allowing them to directly pull up the page that contains the information when you conduct a search.

How Are Search Indexes Created?

Unlike a book index, which a human creates, a search index is built by bots. These tiny bots crawl and index websites to see which keywords are used, turn them into a search index, and make a list that they take back to the search engine.

The search engine then takes this index and places it in its database. Depending on the site's contents and how well attuned it is to Google's algorithms, the site may appear anywhere in someone's search results from page 1 to page 30 and beyond. It all depends on the main search engine's reports from the web crawlers.

Since the crawlers can go over a website regularly, noting any changes that are made, the search index is regularly updated, and the search results can change based on what the web crawlers find.

How Do Search Results Appear?

A search index plays a large role in the search results you receive when you Google search for certain keywords. If you searched, for example, for "dog food," Google's search engines would go through all of their search indexes to pull up the best results.

All of this is done very quickly, in a split second or two, to get the answers you're looking for without taking a long time to go through the databases.

If it weren't for search indexes, those searches would take an even longer time, and the results might be less than accurate.

It's worth noting that search indexes aren't unique to search engines. Federated search systems,specialized or vertical search, and custom internal site search will also leverage a search index and serve results.

What About a Search Engine Ranking?

A search engine ranking is what Google and other search engines create from their web crawlers' information.

There are many things that they look for to give searchers a list of the best quality sites out there; otherwise, instead of searching for "dog food" to pull up a list of dog food companies, who knows what you'd get.

Google updates its algorithms regularly to ensure that the best sites are the ones near the top. Although it changes these criteria and often keeps it quiet so that sites can't use black hat tricks to get their questionable websites to the top of the results, there are some things that it shares.

For example, a website that uses secure socket layers (SSL, or the "s" in HTTPS in the web address) is one thing that is rewarded.

What Exactly Are the Web Crawlers Looking For?

A web search pulls up some very specific information, including the URL of the pages and the keywords that are used on them. These are just a few of the things that a web crawler pulls and adds to the index that it creates. Here are a few others that an indexing search engine will look for:

1. Titles and Headers

Webpages use a variety of titles and headers to break up their content and make it easy to read. Web crawlers note the information and keywords they contain, returning this information to the search engine. How well these headers are utilized can play a large role in the site's overall search engine ranking as well.

For example, they need to relate to the information on the page and include keywords or keyword phrases that the site's owners have discussed in the content.

2. Images

A good website contains a mix of images and text. The images need to relate to the content on the page, enhancing it and helping illustrate what's being said. In order to make it easier for web crawlers to recognize the images, site developers use a mix of image names (titling the image after what it depicts instead of using a generic numbering system) and alt tags.

The alt tags provide additional details about the image, such as reiterating the keywords that it relates to. Web crawlers grab this text and use the relevant parts of it in their indexes.

3. Meta Descriptions

Also known as a site description, a meta description is a short snippet of text that tells the web crawlers exactly what's on the page. These are especially useful in helping customers find information relevant to their query.

Since the meta description also shows up in the search engine results, it needs to be enticing to readers and web crawlers.

Including the required keywords and meta tags is one way to assist them in their information retrieval. It also helps your site's search engine return relevant results since this is one of the many criteria that the algorithms look for and weigh.

Making Your Site Web Crawler Friendly

It's clear that the sites that receive the most attention from web crawlers, as well as the best search engine results, are those that have been properly keyword optimized.

They also have clearly written content, relevant images, and optimized headers and alt tags.

These things play a role in getting a website to the first page of Google's index results for the related keywords. However, there are also a few other things that you can do, such as:

Create Your Own Search User Interface

How a site is built and which pages connect to each other are very important. Although you can't control the web crawlers, you can attempt to influence them by creating and updating your search user interface, including but not limited to your website search box.

This is a method that provides plenty of relevant information on the pages, interlinking them as needed and even ensuring that all of the links are working and that there are no dead pages.

Using a well-organized site architecture and leveraging xml sitemaps, you can make things a bit easier on the web crawlers and point them to the keywords and content you want to rank for. And, if you leverage natural language search, the results will match the intent even when the keywords don't.

Organizations that are lean on resources should consider Search as a Service to build their internal search solution.

Using Analytics

Your analytics, such as those collected in your website's Google Analytics user interface, show you exactly what your site is ranking for. You can find out which readers used what keywords to find your site.

Then, once you have a good idea of what your site ranks for, you can take that information one step further and continue optimizing it to enhance those rankings.

Search tool analytics can be quite helpful in showing you what the web crawlers are discovering on your website and what the average user is searching for on it.

Final Thoughts on Search Indexes

Search indexes play an important role in search engine functions. Without them, search engine results would take a long time to show up, but they might also be inaccurate.

By optimizing your site and making it web crawler friendly, your site will receive the attention and rankings that you desire.

It just takes a little hard work, some good content, and plenty of clever keyword usage.

What to Look for in a Search Experience Platform

Download this eBook for the 10 things you should look for when evaluating search solutions.

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