The Easy Way To Trim Duplicate Pages Via rel=canonical
Having duplicate content on website pages isn't all that uncommon for many types of businesses, especially those with large product or service listings. But that same content could be a detriment for search engine indexation, as pages with substantially similar content run the risk of being penalized by Google's filters (more on that below).
No worries though – Google has created a great article walking businesses through differentiating these pages and reducing any subsequent duplication penalties. It’s posted on the Google Webmaster Tools site right here: http://goo.gl/u8DMuL
Problem is, most businesses don't know it’s out there and aren't dialed into Webmaster Tools. The article also lacks the feet-on-the-street readability that small businesses will open up to, rather than close their browsers to out of frustration with the techno-lingo.
So instead of reinventing the wheel in explaining it, I decided to simply de-tune the already excellent example provided by Google Webmasters Support in hopes of adding clarity for those who are still in search for an answer.
So here it goes:
What is a canonical page?
A canonical page is the preferred version of a set of pages with highly similar or duplicate content – therefore non-canonical pages are the duplicates. Read that again, because it's this very definition that trips most people up.
It's common for some websites to have several pages with content that is very similar to each other. For example, one page might display products sorted in alphabetical order (example 1 below), while other pages display the same products listed by price (example 2), rating, or category.
If Google knows that these pages have significantly similar content, they might index only one version for their search results – permitting their algorithms to select the page it thinks best answers the user's query. Which might not be your preference.
Business owners however can specify a canonical page (think – default page) for the search engines to prioritize by adding a
<link> element within the
<head> section of the duplicate page (i.e. non-canonical). Most website platforms permit this via the admin dashboard or via their CMS - it's the same place you would have added your Google Analytic code. No big deal.
Hang in there – it’s really not all that complicated, in most cases the hardest part is finding where to put the code, not crafting the code.
Adding this tiny string of code is like saying to Google: "Of all these pages with identical content, this page is the most useful. Please prioritize it in search results." How cool is that!
Of the ways to make a canonical URL, below is probably the most common, dear I say nearly ubiquitous:
To specify that http://www.example.com/product.php?item=swedish-fish is the perferred version (canonical) and identifying the others as being substantially similar, create a
<link> element (simple line of code) like the one below and place it into the
<head> section of all duplicate pages (non-canonical versions).
<link rel="canonical" href="http://www.example.com/product.php?item=swedish-fish"/>
Set it and forget it - you're good to go.