Ian Lurie // Sep 30 2009
This is part 2 of a 3-part explanation of basic canonicalization in SEO. Part 1 defined canonicalization and provided examples of the SEO issues it can create. This post shows how to detect a problem. Part 3 will explain how to fix it.
Detecting canonicalization issues is easier (thank God) than defining it.
I usually apply one or all of the following 3 techniques:
This section assumes you’ve already got a Google Webmaster Tools account, and that your site’s verified. If you don’t, or it isn’t, go do it. I don’t care if you think Google is spying on you – they’re doing that anyway. You may as well get the benefit of the toolset.
Here’s how you check for canonicalization issues:
In Webmaster Tools, click ‘Diagnostics’, ‘HTML Suggestions’. Then check for pages with duplicate title tags. If you see a list like this:
…Google’s detecting duplicate title tags on your site. Assuming you’ve used unique title tags on your site, canonicalization is the most likely cause of these duplicates.
For each duplicate title tag, click the ‘+’ sign. If you see two URLs that are really similar, I’ll bet my hat you’ve got a canonicalization issue:
Regardless, click each page URL and view the pages. If the content matches, you’re in canonicalization purgatory:
Record the URLs for every instance of canonical chaos (sorry, couldn’t resist). Google Webmaster Tools makes this easy: You can just click the handy ‘Download this table’ link and get a CSV file.
You can also use a link checking tool and list page title tags. Again, look for duplicates and check for canonical confusion.
If you used the same title tag on every page of your site, then title tag reviews won’t help. Here’s what to do:
This is a very poor method for detecting canonicalization issues, because it’ll detect every single instance of duplication, throughout your site, regardless of the cause. It’s also hit-and-miss, because search engines may actually drop some duplicates.
But, if you click ‘repeat the search’, you’ll get a list of duplicate pages. Then you can sift through the list and check for problems.
You can also build your own site crawler, if you’re a hardcore geek. We did that at Portent years ago, and use it to automatically detect canonical problems.
If you don’t live and breath PERL, PHP or Python, though, I don’t recommend it. You’ll end up like me.
Back to Part 1: Canonicalization defined
On to Part 3: How to: Fix canonicalization problems
Tomorrow, I’ll write about fixing canonicalization issues.
Ian Lurie is founder and CEO of Portent Inc., an internet marketing agency that has provided internet marketing, including PPC, SEO, social and analytics services, since 1995. Read More