The canonical tag was one of the handiest developments in SEO in a long time. It’s thanks to this useful piece of information in the header of our websites that we can essentially eliminate any duplication that might be occurring without needing to go through the development teams to get 301 redirects handled (how many times does it turn out to be a 302?). Unfortunately, as with all things, there’s a lot that can go wrong with them, especially if the people putting them in aren’t quite sure what they’re doing.

If you’ve been in the game for a while, you’ve probably seen some shockingly bad implementations of them. I know I have. Today, I’m going to talk through a few of them.

1. Setting the whole site’s canonical tags to the homepage: this seems to be the most common error with using these tags and it’s a nightmare when it happens. What happens when you set your canonicals to the homepage sitewide? You tell Google and Bing that every page on your site is a duplicate of the homepage and that they should be ignored. Pages disappear from the index, traffic and rankings take a nosedive and everyone in your SEO team collectively bangs their heads on the desk. Please don’t do this.

2. Specifying the wrong page: Another all-to-common error is setting the URL to the wrong page and, tragically, it happens more often than people want to admit. Whether it happens through lack of knowledge, by accident (an uncleared clipboard etc) or another reason, it’s a real pain. In my experience, you get one wrong and it affects the whole site, especially if it’s an important page. Again, the takeaway is just not to do it. Check your work every time.

3. Forgetting to add or remove a trailing slash: similar to the above, this one is very common. The trick to making sure that you get it right is to copy the URL exactly as it’s returned in your browser, but only if you’ve paid attention to the next point

4. Adding page/ session ID’s: This one is a bit rarer, but I still see it a lot on large sites. You tell someone to implement the URL exactly as it gets returned in the browser but the person doing so ends up putting in one of the weird variable parameters that the site throws up – the kind of variable parameters that you’re putting these tags in to get away from. I saw this on a very large brand’s site once, and then they started asking why their new flagship product page wasn’t ranking. Gee, I wonder. Takeaway: put the URL in exactly as it’s returned in your browser, but first make sure it’s the URL you actually want.

5. Not specifying the whole URL: Again, this one happens far more often than I’d like. It’s called the canonical URL tag for a reason – don’t just put / for your homepage, don’t just put /about in your about page either. Put the whole URL in or all the work will be for nothing and, again, heads will meet desks.

The sad thing about this is that I’ve only listed five major canonical tag errors. There are loads of others out there and some of them are potentially even more damaging. I once saw a site which was filled with great content, they have an awesome, well-known brand and yet someone thought copying the canonical tags from another site was the way forward. They actually left the URL of the other site in there!

I suppose the bottom line is to say that if you’re going to put them in place – or ask someone else to do it for you – be very clear about what you expect. Tell them exactly how to use them, what they should be doing and what they should not be doing. The idea behind these things is to make your life easier, not break the site, after all.

I hope you enjoyed today’s guest post. Huge thanks to Tom at Capture Commerce for being an awesome host and I hope you’ll join me on my blog or on Twitter.

Ben Johnston is a professional SEO consultant, copywriter and social media geek. You can keep up with all his news and views from the digital marketing world on his blog at 2 Feet From Freedom.

    2 replies to "The Five Most Common Canonical Tag Errors"

    • emory @ clickfire

      Number 2 seems to occur the most frequently. Canonical tags get set and then forgotten. Next thing you know the specified URL is redirected or even 404’d.

    • Shawn

      I agree with you in saying that there are a lot of canonical errors, however, by just correcting the ones in this post will have a lot of impact on work.

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