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January 28, 2023

What is a Search Index And How Does It Work?

Author imaage
Ahvayita pillai
Associate Growth Manager
Search engine indexing the website content

The internet is vast – there are 1.8 billion websites online and every site has its own unique content. In this scenario, understanding how to locate information is a challenge.

Search Index

How to find what you’re looking for?

Search engines provide the answer by using something called a search index – it’s like your own personalized library of all documents online.

Think of it this way: when you walk into a huge public library with thousands of books, finding one particular book can be tremendously difficult. This is where a catalog comes in – it’s an organized list of all the books the library has, sorted by author and title.

A search engine index works similarly. What exactly is a search index, and how does it work? We break it down below. 

What is a search index?

Search indexes are databases that search engines use to catalog websites and their content. 

In simpler terms – an index of all the information on the internet or on a website.

Think of it like a giant card catalog – instead of books, though, it’s websites. Search indexes create a massive database with records for each webpage on the Internet (just like each book in a library). The index stores the most important information about each page and files it so that when you search for a topic, relevant results can be found quickly.

The index is used to determine what results to show a user when they submit a query.  The search engine checks its index for all the information that relates to a query – and viola, there are millions of results!

How does that help people find what they need?

Let's say you have a website about cooking. You add a new recipe for Thai green curry to your site. Once the search engine crawls your site and sees the new content, it adds that page to its index. 

Now, when someone searches for "Thai green curry recipe," your website's Thai green curry page will show up as a result. However, that page wouldn't be returned as a result if it wasn't in the index. 

The search index is at the heart of every search engine. It’s what makes it possible for a user to enter a query and receive relevant results in return. Without a search index, there would be no search engine. 

How does search indexing work? 

A search engine “crawls” the internet, it looks at all the websites out there and creates an index based on what it finds. It takes into account things like the website’s content, how often it’s updated, how many other websites link to it, and more. 

Take Google as an example. It’s the most popular search engine and has one of the largest indexes in existence; their index comprises  over hundreds of billions of individual webpages and is over 100,000,000 GBs in size! To build such a massive catalog, search engines use a process called web crawling where automated robots scan through all publicly accessible websites and index their contents.

Bringing it back to the library analogy, it’s like a librarian walking through the stacks, reading each book one by one in order to file them into the catalog. The bots then store information about these websites for easy retrieval – things such as text content, images or videos, and metadata.

When you search for something on a search engine, it’s this index that powers the results page. The query is sent off to the index where relevant records are found and ranked according to a complex set of algorithms (which determine which sites show up first). When you click on a result, the index sends you to the correct webpage.

Search indexes are essential for modern search engines; without them, we’d be stuck searching through millions of webpages one by one in order to find what we’re looking for. 

Thankfully, these powerful catalogs exist and make our online lives much easier.

In the age where everything from shopping to news consumption is online, search indexing plays an even more crucial role. 

Digital enterprises of all sorts depend on search engines, and in turn indexes as a core part of their business.

Firstly, companies need to ensure that their websites are optimized for search engines in order to maximize visibility. 

Nearly three-quarters of all internet traffic begins with a search, which means that if you want people to find your business online, you need to make sure you show up in search results.

Search engine optimization (SEO) is a process used to make sure webpages rank highly in organic searches on major search engines. SEO professionals work to optimize content and code to make sure it’s easily found by search engine crawlers, greatly increasing the website's chances of appearing on the first page of Google or other search results pages (SERPs).

Secondly, an effective search index can help increase sales or market share by directing customers toward the most relevant information, products or services. An optimized index will make sure that when customers look for a specific item, they’ll find what they’re looking for quickly and easily.

An ‘effective search index’ will mean something different for different businesses.

For example; for ecommerce businesses, it's essential that customers find what they want to purchase as easily as possible. While, for media companies, a well-maintained search index is essential to ensure that news articles or videos are accessible for readers and viewers. A proper index will make sure the latest stories remain at the top of search results pages so audiences can stay informed in real-time.

Or, an internal search engine for businesses like banks and financial institutions is necessary to secure customer data. A thorough catalog of all sensitive information can help companies stay compliant with industry regulations while protecting their customers’ privacy. 

In short, regardless of the industry or type of online business – having an optimized and up-to-date search index is essential for success.

How do search indexes rank pages?

Search indexes rank pages based on a number of different factors. As we mentioned before, what matters and what’s effective will look different depending on the purpose of the search index. So for an ecommerce website factors like sales rank, and customer reviews might be of prime importance, while for media companies, factors like authority, relevancy, and how important the news is would take precedence.

In general, though, search indexes judge relevancy – the amount of content that’s related to what was searched for, and the quality of content – so that irrelevant or low-quality pages are pushed down in rankings and higher-quality pages appear first.

Search indexes are useful for all types of online businesses, from media companies to e-commerce stores. They can help make sure that websites are optimized for search engines and that customers can find what they’re looking for quickly and easily. 


Search indexes transformed the internet from a digital wasteland into the wealth of information we have today. And for businesses, they’re essential for being found online and driving traffic – and sales – to your website. If you want to make sure people can find you when they search, you need to understand exactly what search indexes are, how they rank your website, and how you can utilize them in your business. 

No matter what industry you operate in, or what kind of customers you cater to, your search index needs to be able to adapt to wildly different factors and customer needs. If you’re looking for a search engine that displays results factoring in context, meaning, and optimum industry factors, – Zevi’s AI-powered search is here for you. Book a demo with us today.

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