Does Duplicate Content Affect SEO Promotion in Google?

Today we will talk about duplicates and how they affect the SEO promotion in Google. One of our subscribers asks: "I am interested in your opinion on duplicate content in regards to Google, how does it affect the promotion of the site? And how to delete duplicate content if needed?" 

How Google Treats Duplicate Content 

In general, Google doesn't take too kindly to duplicate content. This is especially evident when you start creating any regional versions of sites on subdomains or on subfolders. Google recognizes that the content is pretty much the same with the only change being the toponym. Site pages usually enter the index, but they are not ranked. And this happens in many situations with duplicate content inside the site. 

However, the search engine does not always treat duplicate content from other sites the same way. That is, if you copied content from another site, but also added some additional value to it by including some changes, then in that case Google will rank it pretty well. Aggregators are a good example. In the Telegram channel dedicated to my SEO courses, I demonstrated how we launched an aggregator website, and by the third month, it started gaining 6.5 thousand traffic per day from Google despite the fact that the content there was entirely taken from other projects. All of this means that it's not that clear-cut. But Google doesn't really respect duplicate content inside a site and chooses the main version of these pages and sends traffic their way, ignoring the rest. 

In addition, there is also an effect that does not always occur, but it happens when two events go hand in hand: when duplicates are made in the site (usually the regional ones) and after a while after this the main version of the site is affected. This does not happen very often, but I've had a couple of such cases. We analyzed them, and in the end, each time there was a more compelling reason why there was such a low ranking. Nevertheless, this happens, and many SEO experts believe that this is not just a correlation, but interrelated events. So being careful about this wouldn't hurt.  

To sum up, Google doesn't like duplicate content within your site. It also applies to the cross—site duplicates, too. If there is not enough value in the content, then the pages often have problems. However, this doesn't always happen — there are exceptions from each case, sometimes full duplicates happen to rank pretty well. 

How to Delete Duplicates the Right Way

If you have definitely decided that you want to delete one of the versions of your duplicates, then you have a variety of options: 

If this is a section that can be found based on its URL address, then you can put it into disallow: type "disallow" in the robots.txt file with a prefix of these addresses;  the second option, which is  is to do redirect 301 to the main versions of your duplicate pages, is more reliable. This method is more correct, because it is possible that some traffic was already going to those pages, people went there, some links led there. And to save all that, I recommend not closing it, but using redirect 301; 

rel canonical. If for some reason you can't use 301 (let's say you still want to leave these pages to users), then put the rel="canonical" tag in <head> , where you enter the main address of the page. Google usually respects and adheres to it; 

You can close it in a more reliable way than robots — using the robots noindex meta tag or the X-Robots-Tag in the HTTP header. 

Here are four other ways of doing this, though I still recommend using redirect 301 first and foremost. Canonical takes the second place after redirect 301, X—Robots-Tag or noindex meta tag is in third place, and closing it in robots.txt is in fourth. These are pretty much the main ways of closing duplicates.