How misunderstanding the canonical tag could ruin your SEO
What’s a canonical tag?
The canonical tag is a little piece of code that sits in the header of your web page (between the <head> and </head> tags) along with your meta tags, and it looks something like this:
<link rel=”canonical” href=”http://thebluecube.com/blog” />
The purpose of this tag is to let search engines know that the content from the page containing the tag is taken from another page on the site. This means that instead of being penalised for duplicating your content, a search engine will instead index only the page referenced in the canonical tag instead of trying to index duplicates.
Sounds great! Should I be using it?
It depends. If you’re still not sure by the time you’ve finished reading this article, I suggest you consult a professional web developer or SEO provider to make sure your SEO effort isn’t being jeopardised.
A great example of when to use the canonical tag is for an e-commerce site. Many large e-shops have a complex category-based structure which helps users to find the products they’re most interested in. Say for example you have a stationery shop. Your prospect is looking for a recycled hardback A4 notebook. There are three routes he could take to find this item because there are separate categories for A4 notebooks, hardback notebooks and recycled notebooks (it’s a big store!) Chances are, the URL for the page showing the desired book will differ depending on the route taken to find it.
This is where the canonical tag should be used. Choose a ‘main’ page for your product, and then be sure to include a canonical tag showing the main page URL on any other page duplicating this content.
Even if there’s only one path to your page, you may still experience duplication issues if your website uses a session or tracking ID in the URL, or a search-filtering URL.
How does this improve my SEO?
Put simply, Google and the other search engines ‘frown’ on duplicated content within a single website. Identical or near-identical content creates the problem of selecting which pages to crawl from spiders’ limited bandwidth allocation, and which to recommend when someone searches for your content. Correct use of the canonical tag means you’ll benefit from a more comprehensive understanding of your site and its content by the search engines. This means better rankings and more accurate search results.
So what can go wrong?
When the canonical tag was first introduced, many website owners misunderstood its purpose, and included it on every page, referencing their home page like so:
<link rel=”canonical” href=”http://thebluecube.com/” />
They mistakenly thought it would identify any given page as ‘belonging’ to their site, thus creating more credibility by association. And how they suffered.
By using the tag in this way, they were basically telling search engines that every page on their website was a duplication of their home page. This effectively condensed their whole site’s value into a single page. So much so, that their other pages often never even made it into the SERPS.
Understanding is the key to success
In short, only certain kinds of websites need to use this tag. If your site has only a handful of unique pages, you’ll never need to use it. But if you run a complex database-driven site with dynamic URLs, you should look closely at how content may be duplicated across your site, and carefully apply the canonical tag to ensure only a single page is indexed for any duplicated content.
About seoblogger:
Our SEO blogger is an expert in Web Marketing, Usability and Interface Design. He has been a vital part of The Blue Cube Communications since 2003. As the West Midlands fastest growing web marketing agency, we always strive to maximise return on investment for our customers.
