Does Google Detect Duplicate Content If Every 13th Word is Unique?


Andrew Steven
August 9, 2019


In one of our last blog posts, we scientifically proved 51% / 49% (unique to duplicate content) to be the minimum ratio required for a page to be determined unique. Our test was designed to find a “sweet spot” of words on a page - that number which would make a page unique in the eyes of Google. To that end, we ran 5 tests, each with its own target keyword. The goal was to compare 2 pages (Page A and Page B), each with a different percentage of duplicate content, and figure out the optimal percentage of unique text for various cases. Page A was indexed first; Page B was then indexed to test whether it was read as duplicate content.

We concluded that regardless of how many words are used the ratio appears to be the deciding factor. For instance; 100 unique words and 100 duplicate words are considered unique overall, whereas 400 unique words and 800 duplicate words are considered duplicate and wont index.

This experiment was run about a year ago. But we decided to take the results of the previous tests a step further to examine whether Google detects duplicate content if every 13th word is unique. Essentially breaking up a big block of duplicate text with single, unique words. 

If you've been in SEO a while, then you know this was one of the original 'google leak' rumors. What do you think? Will this rumor sink or swim?

We set up the test like this..

This experiment was an extension of our previous experiments on duplicate content. In the previous experiment, we determined that if 51% of the page consists of unique content, it will be considered unique overall by Google. 

The current experiment was run in a few different ways to prove our new Hypothesis. 


If every 13th word is unique, the page will be considered unique overall. 

We set up five pages, each optimized for the same keyword and ran the tests five times. 

All five pages were identical except for one difference: the position of the target keyword + a unique word on the page. Page 1 was left unchanged. On page 2, the target keyword + a unique word was added every 6th word. Page 3 had the same settings as the previous two pages except for adding the target keyword + a unique word every 13th word. On page 4, the target keyword and a unique word were added every 24th word. The last page tested had the target keyword and a unique word added every 4th word.

The idea behind setting up the tests this way was simple: if the page is not unique enough, it will get filtered. If Google detects duplicate content, a message (shown below) will be displayed at the bottom of the SERP:

Here is what we discovered

The results of the five tests were astonishing: all five pages appeared in the SERP with no duplicate content issues.

Even Page 4, which had a unique word every 24th word - seemingly the most un-unique, still passed the duplicate content filter.

Final Takeaway

We actually discovered that it’s enough to have every 24th word unique in order for Google to see your page as “unique” and not de-index it. 

Disclaimer: This experiment was not done to “trick” Google. And we most certainly do not encourage you to spin content. Rather, our goal is to show the science behind Google’s algo. Even with no duplicate content “penalty,” it is widely accepted that Google rewards quality and unique content that brings value to the viewers. 

About the author 

Andrew Steven

Andrew has been building and managing SEO teams since 2008 where he led the largest SEO firm in Australia. Since meeting Kyle and partnering to form High Voltage SEO Andrew has been Kyle Roof’s man behind the scenes and together with Maria Dubretic have since co-founded the SEO tool PageOptimizer Pro. Andrew wishes he could stop dreaming about digital marketing in his sleep and would love to hear from anyone who has a cure for this.

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