What are LSI Keywords? And Why They Matter For SEO [New Guide]

Content Optimization Strategies

LSI Keywords

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LSI Keywords

What are LSI Keywords?

LSI (Latent Semantic Indexing) Keywords are conceptually related terms that search engines use to deeply understand content on a webpage.

Why are LSI Keywords Important?

In the early days of SEO, Google and other search engines would figure out a page’s topic based 100% on the keywords they found on the page.

Google used to only look at keywords

So if Google saw the keyword “Content Marketing” over and over again, they’d say: “This page is obviously about content marketing”.

Just repeating keywords used to be effective

That’s why keyword density was so important back in the day.

If you didn’t use your keyword bunch of times, Google wouldn’t understand that your page was about that term.

Fast forward to today, and Google is MUCH smarter.

Today, Google’s goal is to figure out a page’s overall topic.

Google now aims to find the overall topic

And Google relies on LSI keywords to understand content at such a deep level.

For example, let’s say you just published a blog post about cold brew coffee.

Google will still scan your page to see if you use the term “cold brew coffee” in your title tag, content, image alt text, etc.

Google still scans key areas of your site

But they’ll also scan your page for LSI keywords (like “filter”, “temperature”, “grind”, “cold water”, and “ice”).

Google can also scan for LSI Keywords

And when they see these LSI keywords in your content, they’ll say: “We’re confident that this page is about the topic of cold brew coffee.”

LSI Keywords add up to let Google determine the topic

In fact, a recent Google research paper states that they use “words frequently occurring together” to understand an article’s main topic:

Word clustering

One thing I should point out:

LSI Keywords are NOT synonyms.

Instead, they’re terms that are closely tied to your target keyword.

For example, take a word like: “jogging”.

Well, “running” is just a synonym of “jogging”.


There’s nothing wrong with using that synonym in your article (in fact, it can help with your on-page SEO).

But it’s not an LSI Keyword.

LSI keywords for “jogging” are things like: “shoes”, “cardio” and “5k”.

With that, here’s how to find LSI keywords.

Best Practices

Google Autocomplete

Google Autocomplete is one of the fastest and easiest ways to uncover LSI terms to use in your content.

For example, I recently published “The Ultimate SEO Site Audit”.

Backlinko SEO Site Audit Post

And to optimize that page, I typed “SEO Audit” into Google.

Google SEO Audit

And paid attention to the bold words that it suggested to me.

Google Suggest – LSI Keywords

These bold words are LSI Keywords.

After all, they’re terms that human users search for when they search for anything related to “SEO Audit”.

So I included those terms in my content:

Terms in content

You can also try Keyword Tool and UberSuggest.

Keyword Tool and Uber Suggest

Both of these tools give you A LOT more suggested keywords than doing things the old-fashioned way.

Uber Suggest – Results

That said, Google tends to suggest the most popular (and therefore most relevant) terms right off the bat.

So I usually only use one of these tools if I want to optimize my content to the max.

LSIGraph and LSIKeywords.com

Speaking of tools, there are a few tools that specifically generate LSI keyword ideas: LSIGraph and LSIKeywords.com.

LSIGraph and LSIKeywords

They both work pretty much the same way.

You type in a keyword that you want to rank for…

LSIGraph – Results

…and get a list of LSI terms that you can include in your content.

They’re both free SEO tools. So you can’t go wrong with trying out both of them.

(Although I should point out that LSIGraph does have a paid plan… so it’s technically “Freemium”)

Overall, I think both tools work great. But if I had to pick one, I’d have to go with LSIKeywords.com.

It tends to give me more closely related terms that aren’t straight up variations of my target keyword.

For example, when I type “SEO tools” into LSIKeywords.com, I get tons of related terms (like “Google Analytics”) that make PERFECT LSI keywords.

LSIKeywords – "seo tools" results

“Searches Related to…”

“Searches Related to…” is similar to Google Autocomplete.

But instead of Google suggesting keywords as you search, they give you related terms at the bottom of the search results.

Searches Related To SEO Tools

For example, this list of SEO tools is one of my high-priority pages:

Backlinko SEO Tools Post

And considering how insanely competitive this keyword is, I know that I need to nail my LSI… or I have little to no chance of rankings.

That’s why I searched for “SEO Tools” and scrolled down to the bottom of the page.

Searches Related To SEO Tools

Then, I identified bold terms that made sense for my post.

Keywords In Searches Related To

And included those in my content:

Keywords collage

Simple, yet effective.

Bold Terms in Google Snippet Descriptions

This is another way to find LSI Keywords directly from Google.

You might have noticed that Google bolds terms in result snippets that match your keyword:

Bold snippet

And if you look closely, you’ll notice something else:

Google doesn’t ONLY bold terms that exactly match what you just searched for.

They also bold words and phrases that are similar.

For example, let’s look at the results when you search for “PC Repair:

"PC Repair" SERPs

Yes, Google bolds the exact term:

Exact term

But they also bold related terms, like “Computer Repair” and “PC Fix”:

"Computer Repair" highlighted

Needless to say, these are LSI keywords that you want to sprinkle into your content.

Google Keyword Planner

The Google Keyword Planner is still one of my favorite keyword research tools.

Google Keyword Planner

As it turns out, the Google Keyword Planner is also an LSI Keyword MACHINE.

For example, if you put “SEO Tools” into the GKP, you get a list of “Keyword ideas”:

Google Keyword Planner – Results

Some of these will be synonyms and variations of your keyword:

Google Keyword Planner – Highlight

But if you dig deep, you can find some sweet LSI phrases that you’d be hard pressed to get any other way:

Google Keyword Planner – Dig deep

Pro Tip: you don’t need to enter a keyword into the GKP. You can also use a landing page.

Specifically, you can use a competitor’s landing page that’s ranking above you in the search results.

Google Keyword Planner – URL search

When you do, Google will scan the page and spit out keywords that they consider relevant to that page’s topic.

Google Keyword Planner – URL results

(In other words: LSI Keywords)

Google Image Tags

This is a new feature inside of Google Images that I don’t see a lot of people talk about.

And it’s an LSI goldmine.

To use it, just pop your keyword into Google images.

Google Images search

And Google will hook you up with a bunch of related terms above the image results:

Google Images suggestions

You can do the same thing with Pinterest (in fact, this is where I first saw this feature used).

Pinterest image suggestions

But these suggestions don’t come from Google. So now I stick with Google Images.

Use LSI Keywords Throughout Your Article

Now that you have a list of LSI Keywords, how do you use them?

I’ve tested this quite a bit.

And my takeaway is: it doesn’t really matter.

In my experience, as long as Google sees these terms somewhere on your page, you’re good.

So feel free to include your LSI terms:

  • In your title tag
  • In image alt text
  • As a H2 or H3 subheader
  • In your H1
  • In the content itself

For example, I published this guide to learning SEO a few months ago:

Backlinko – Learn SEO Fast Guide

And one of the “Searches related to…” keywords that I found was: “basics”.

Searches related to – Basics

So I included that term in my content a few times:

"basics" in content

That’s all there is to it.

Learn More

Semantic SEO: Everything you need to know about Google Hummingbird and Semantic SEO.

How to do “Semantic SEO” in 8 Minutes: A very actionable video that demonstrates a lot of the techniques I’ve outlined here.

Latent semantic analysis: Wikipedia entry dedicated to some of the technology behind LSI. Super dense but worth reading if you want to understand the “why” behind LSI keywords.

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