Duplicate content

When pages are largely or completely the same, that is duplicate content. It makes it hard for search engines to pick the right page to show a searcher.

Misconceptions about duplicate content

A stubborn myth says duplicate content harms your website. That is not quite true: Google does not hand out penalties for duplicate content. It can, however, make your site harder for Google to index. Hard enough that it can lead to lower rankings.

How does Google handle duplicate content?

In principle, Google indexes each page only once. When it finds duplicate content, it decides which of the two pages to keep in its index. Google may keep the wrong one, and you can end up competing with yourself.

Causes of duplicate content

Duplicate content has several causes. These are the most common ones.

www vs. non-www

Sometimes a website works both with and without the www subdomain. www.example.com and example.com then show exactly the same page, and Google has to choose which one to index. A 301 redirect or a canonical tag fixes this easily.

http vs. https

Good, your site works over a secure connection. Now make sure you redirect the insecure version to the secure one. That way Googlebot knows for certain that everyone should go to your secure site.

Filter pages

In a web shop you can usually sort products by all kinds of properties, such as price, size or color. The exact same products then appear in a different order. Google recognizes that this is really the same page. A canonical URL solves it.

Thin content

When a page has very little content, Google has a hard time telling the content apart from the template around it. If many of your pages are thin, take a look at your content strategy.

Copied pages

Copying pages from others is simply not done, and Google agrees. Have you copied pages from other sites? Remove them and write your own unique content. If you really need to reuse someone else's content, at least give them credit with a link and a canonical URL.

Finding duplicate content

Finding duplicate content by hand is hard work, but for a machine it is not difficult. There are several tools that find duplicate content within your own site. Others, such as Copyscape, can even find duplicates of your pages on other sites.