How Keyword Density Impacts Search Engine Optimization

Like many SEO practices, keyword density is a moving target. The rules keep changing over time.

Keyword density is an SEO tactic that suggests how many times a particular keyword should appear in a document. Locations in a document include its title, meta description, headline, body copy, image name, image caption and image alt tag, among other opportunities.

A keyword that appears too many times will make the document read in an unnatural way and run the risk of getting a spam penalty. (When I say keyword, I also mean a keyword phrase of two or more words.)

A keyword that appears only once may weaken its results in search engines. A single appearance suggests the article doesn’t emphasize the keyword topic. Multiple uses will show an emphasis on a topic, but multiple uses has a limit.

Measuring Keyword Density

One way of measuring keyword density is by counting the number of times it appears on the document in all places and dividing the number by the total number of words in the document.

For some time, it was commonly accepted that a density above 2 percent for some search engines and 5 percent for others was a red flag about spam.

That’s no longer the case, according to Matt Cutts, former head of Google’s Web spam team.

“The way that modern search engines, or at least Google, are built, is that the first time you mention a word, you know, ‘Hey, that’s pretty interesting. It’s about that word.’ The next time you mention that word, ‘oh, OK. It’s still about that word.’

“And once you start to mention it a whole lot, it really doesn’t help that much more. There’s diminishing returns. It’s just an incremental benefit, but it’s really not that large,” Cutts says.

So the rules about having the keyword appear too often don’t seem to matter as much anymore. Now it’s a matter of having it appear X number of times in X locations on the document. Still, it’s best to avoid using a keyword too many times because it makes the reading of the document unnatural or awkward.

What also matters is whether “ghost” keywords dilute the true theme of the article. Ghost keywords are repeating, unintended keywords that compete with the intended ones.

Why Keyword Density Still Matters

It doesn’t require top-secret access to the Google algorithm to know one completely logical idea:

Density combined with prominence matters a lot.

Cutts says the first time you mention a word, the search engines know at least part of the article is about that word. That part may only be a sentence or paragraph.

What if the most important keyword doesn’t appear in the title? The search engines may think the document is about something else.

What if the keyword appears in the title along with another keyword?

Then the search engines might not be sure if the document is about the first keyword or the second.

Density becomes important again. If the primary keyword appears a second time, such as in the first paragraph of the article, the search engines will have a better idea that it’s about the first keyword and not the second.

A document with 20 repetitions of a keyword doesn’t matter. A density of “more than one” will create clarity for search engines.

Just as importantly, a keyword that appears in the title, file name and meta description is more likely to get a response from searchers.

So yes, density still is important. It’s the execution and consistency of execution that counts.

Tip: As a rule of thumb, trying including the keyword at least once out of every 200 words.

How to Check for Keyword Density

One simply way of course is by scanning through the article and counting the number of times it appears.

But there is a better way, which is using one of the many tools available online to check for density.

For example, do a search on “keyword density” on Google. For my search, the first link in the search results goes to a keyword density tool on the site SEObook.com.

When I enter this article into that tool, I discover that “keyword density” appears eight times in the article.

But “search engines” appears seven times, almost as much as my article theme.

Is my article about the first keyword or the second one?

Therein lies the advantage of using a KD tool — to identify competing keywords and clarify the article topic for the search engines.

It’s another reason to make sure that the dominant keyword appears in the article title, meta description and other prominent locations.

As a result of adding more content, my main phrase now appears much more often than the “search engine” keyword phrase.