What is LSI – latent semantic indexing?

Most probably you have already heard about LSI (Latent Semantic Indexing) and its applications in SEO optimization of a website. However, its acronym tends to get a bit scary and we shouldn’t be surprised if, after all, there are few people who really understand what it is and how it can be really useful for a website.

In this article we will try to explain in simple words what this LSI is and what it has to do with SEO. We will also explain why, according to some, latent semantic indexing should have nothing to do with the SEO world.

What is LSI?


We will stay on topic and answer the main question immediately: LSI is an indexing method.

DO NOT GET ME RASH, I AM NOT DESCRIBING Google’s indexing METHOD, but rather a mechanism that is part of indexing.

An SEO novice might think that, to find an accurate resource in the network, a search engine looks for the precise query entered by the user in the various published documents, returning only exact matches. In short, if you were to search for the word “Thermopane”, Google would only and exclusively return resources containing that given word. In reality, Google is much smarter than that, looking for relationships between different documents, which therefore go beyond the simple repetition of a keyword.

This means that if you type in “window frame”, Google would search not only for words containing window frames, but also for all semantically related words such as “windows”, “window frames”, “windows and doors” and so on.

I have just briefly explained what latent semantic indexing means.

It must be said that this is nothing new, on the contrary: the LSI technique was hypothesized in the 1960s and patented in 1989. It is not new, however understanding how latent semantic indexing works, in our opinion, can greatly help anyone who wants to optimize a website, from the SEO expert to the content creator of a small blog.

Latent semantic indexing and SEO

The first and fundamental consequence of learning how the LSI indexing method works is to understand that the forced repetition of keywords in web text does not make much sense. Why make a text artificial and cumbersome by stuffing it with the same keywords (keyword stuffing), when instead we know that search engines are able to “understand” what we are talking about by comparing our page with other texts on the web?

It is wrong to think of Google as a search engine that only looks at the keyword or, rather, only looks where we tell it to look. No, Google reads all our pages, to steal every word, to give your users better results.

Therefore, continuous and forced keyword repetition is useless. Better to write more natural texts, using more synonyms and all related terms that might be useful for the user, using extensively – why not – the precious long tail keywords.

On the net we often talk about the best methods to find keywords according to the LSI technique. To do this, you can rely on the same Google tools, such as Google Autocomplete suggestions (i.e. the autocomplete that the search engine gives us when we enter our query in its search bar) or even the indispensable Keyword Planner.

Finally, there is a tool specifically designed to find keywords and thus take advantage of latent semantic indexing: we are obviously talking about the LSI Keyword Generator portal (unfortunately only available in English).

LSI and SEO: Not everyone agrees

There are some SEO experts who argue that LSI doesn’t matter for SEO optimization. Everyone knows that the LSI indexing method was fundamental to the development of search engines. However, others say that there is no certainty or evidence that today’s search engines still use this method.

On the other hand, it is true that, for those involved in creating SEO-optimised content, considering the LSI indexing method is extremely useful: because this way we can create better, more natural, richer content, both for users and for search engines.

Latent Semantic Indexing (LSI) keywords are terms and phrases that are semantically related to a main keyword. In other words, they are words and phrases that are closely related to the topic of the main keyword and provide context to search engines. In this article, we will explore the importance of LSI keywords for SEO and how to incorporate them into your content strategy to improve search engine rankings.

Why are LSI Keywords Important for SEO?

Search engines use LSI keywords to determine the relevance and context of a webpage. The more LSI keywords a webpage contains, the more likely it is to rank higher for a particular keyword. This is because search engines are able to understand the meaning behind the words on a webpage, which helps to determine the relevance of the page to a user’s search query.

How to Incorporate LSI Keywords into Your Content Strategy

  1. Research LSI keywords related to your main keyword. There are several tools available to help you research LSI keywords related to your main keyword. These include Google’s Keyword Planner, SEMrush, and LSIGraph. Simply enter your main keyword into the tool and it will generate a list of related LSI keywords.
  2. Use LSI keywords throughout your content. Once you have a list of LSI keywords, it’s important to incorporate them throughout your content. This can be done by including them in headings, subheadings, body text, and meta descriptions.
  3. Use synonyms and related terms. In addition to using LSI keywords, it’s also important to use synonyms and related terms throughout your content. This helps to provide even more context to search engines and increase the relevance of your content to a user’s search query.
  4. Optimize for readability. It’s important to remember that your content should be written for your audience, not just for search engines. Therefore, it’s important to ensure that your content is optimized for readability and is easy for your audience to understand.


In conclusion, incorporating LSI keywords into your content strategy is a critical aspect of optimizing your website for search engines. By researching and using related keywords throughout your content, you can improve your website’s relevance and visibility in search results. Remember to also focus on creating high-quality, readable content that provides value to your audience.