A Guide to Canonical Tags & How to Use Them

If you want to be found on the internet, you need to make sure that your website is optimised for Google’s algorithm. There are important ranking factors to help Google notice and reward your business with high search rankings, and one of these is canonical tags. Let’s break down what these are, and why getting on top of canonical URL best practices is so crucial for your success in the digital marketplace.  

What is a canonical tag?

Google hates duplicate content, and will automatically index just one web page if it finds multiples, making a decision on which page is the original. The thing is, you don’t want Google making this call for you. The algorithm won’t necessarily get this right, and leaving it up to chance risks undoing the hard work you’ve put into search engine optimisation in other areas. A canonical tag is a small piece of HTML code, which is implemented in order to indicate to search engine crawlers which page they should take as the original, and ensure that your efforts to improve SEO aren’t cannibalised by duplicate content on other pages. 

What does a canonical tag do?

When the same or similar content appears on multiple pages, providing a canonical tag (rel=”canonical”) in the metadata of a URL indicates to Google which page you want to be crawled and indexed, and means you’re in control of deciding which web page contains your most important content. It signposts to Google which page is the one to count, and expedites the process. 

Even if you don’t think your website has duplicate content, the fact is it almost certainly does. User sessions, product filters, capitalised letters, serving content at locations with and without www, all of these instances create what’s called parameterised URLs, which Google technically categorises as separate, and therefore duplicate pages. 

How canonical tags can be helpful for SEO

Canonical tags aren’t just nice to have, they’re an essential part of an effective technical SEO strategy. With CMSs, http and non-https variants of the same page, along with mobile versions, you can quickly start racking up duplicate versions of pages. Canonical tags can be used to make sure your SEO doesn’t suffer because of this. Here are just a few reasons why. 

You choose the canonical tag

Especially if you’re using a CMS (content management system) like WordPress or if you have a separate mobile site, you may find that different pages with the same content end up having discrete URLs which aren’t the same. By far the easiest and fastest way to make sure that Google indexes the URL you want is to choose that version for it, using a canonical tag. Being proactive in this regard avoids any potential penalisation by the algorithm.  

Duplicate content can spoil your rankings 

The problem with duplicate pages is that, as we mentioned, Google really doesn’t like them. For it and other search engines, it’s an indicator that a site isn’t producing unique, high quality content, which it views as an indicator of authority and trustworthiness. Especially if you run an eCommerce store, but for any website, duplicate content can start to outrank the page you want getting the top spot on Google, and can even risk Google missing some of your other content as it crawls non-canonical duplicates. 

Crawl budgets aren’t limitless

A crawl budget refers to how many pages of your website a search engine will crawl on your site, and how quickly it wants to do it. If you have lots of duplicate content, but you haven’t nominated a canonical URL, your crawl budget may get wasted as Google searches through duplicate content instead of indexing the other valuable content you’ve produced.   

Consolidated link signals have more impact

Bringing your link signals onto one consolidated page can help you improve the ranking for that canonical URL, rather than splitting up your ranking power across lots of similar pages. There are five types of canonicalisation signals: 

• HTML tag (rel=canonical)
• HTTP header
• Sitemap
• 301 redirect*
• Internal links

A link signal is basically a way to tell Google that all similar content pages are linked back to their parent page — the canonical one. By making sure all link signals point back to the page with a canonical tag, you boost this page’s chances of hitting the top spots on Google. 

Best Practices

Okay, so we’ve convinced you that canonicalised URLs are the way to go – so what’s the best practice when it comes to setting up canonical tags across your online content? Let’s get into it. 

Canonical tags can be self-referential

In fact, they should be. Self referencing tags reference the URL of the given page itself, and this avoids any confusion on Google’s part. While it’s not completely necessary to do so, the fact is that Google experts recommend this as best practice, because it makes it crystal clear which page you want to be indexed.

Canonicalise cross-domain duplicates

If you’re syndicating content, canonical tags also stop cross-domain duplicate issues from arising. Using a cross-domain canonical tag will reduce the risk of any incidents of syndication outranking your original content, and make sure that you earn the authoritative reputation you deserve.  

Be careful in canonicalising near-duplicates

The point of canonical URLs is to clearly indicate the preferred version of a web page, and to designate it as the definitive version to be counted by search engine crawlers. If you have near duplicate pages, and you’re tagging them both as the canonical version, your efforts will start to become self-defeating. The best practice for canonical tags is to only ask the algorithm to find and reward one example of the content, so avoid overdoing it when tagging pages which are substantially similar or near duplicates.  

Avoid mixed signals

You want your link signals on duplicate and similar pages to uniformly point back to one canonical URL. If you start to use mixed signals, Google’s algorithm can become confused, and your rankings will suffer. Again, the point here is to make it simple for Google to reward your other search engine optimisation efforts, so it’s best practice to choose one of the five canonicalisation signals, and be consistent when using it across your site. 

Spot check your dynamic canonical tags

Regular website audits are also best practice, for a whole number of reasons. No matter how carefully you update your website and add new pages, products or content, the fact is dynamic canonical tags can become untethered from their original purpose. Make sure you regularly perform spot checks to make sure these technical aspects of your SEO are in good shape and are getting you the results you want.   

The basics of canonical tag implementation

Once you’ve got the best practices for applying canonical tags down, you’re ready to start streamlining your website for Google and other search engine crawlers to find and reward your most authoritative content. Before you start applying rel=”canonical” to every URL, there are some basic issues you’ll want to avoid when it comes to implementation. 

Avoid canonical loops and chains

Imagine that a canonical tag acts as a trusted expert who ‘endorses’ the right version of a page for the benefit of Google. The algorithm is looking for a sign from this expert that says, “Hey! I’m page Y, but the best source of this content is actually on page X. I recommend you visit page X and hear what they have to say!”. “Great”, thinks Google’s crawler, and it heads over to page X to start indexing away. Now, imagine that page X also has a message for Google, which is “Hi! I’m page X, but you actually want page Z”. Google then heads to page Z, which agrees that it is the best version of the content. 

This is a canonical chain, and if you just felt some confusion reading that, imagine how quickly it can bamboozle a machine primed to trace canonical tags back to one trusted source. Chains, like the one illustrated in that example, and loops, where canonical tags send search engine crawlers in a circular motion from page X to Y to Z and back to X again, are going to completely undermine your efforts to help Google’s algorithm reward your best content. 

Don’t block canonicals via robots.txt

As part of technical SEO frameworks, a robots.txt file will help search engine crawlers know where to go and not to go within your site’s architecture. If you disallow URLs in robots.txt, it can’t tell Google and other search engines to read your canonical tags, and it won’t consolidate link signals from different pages. To make sure your tagging efforts are rewarded, ensure canonical URLs are allowed via robots.txt files. 

Multiple canonicals on one page

If you use more than one canonical tag on a page, Google will simply ignore them both. This isn’t a crude tool which can be sprinkled liberally throughout all of your metadata for infinite search engine optimisation. Be strategic when using canonical tags, and you’ll be that much more likely to make sure they work in the way you want them to. 

What to avoid with canonical tags?

Canonical tags are best deployed when you have lots of URLs with very similar or identical page content. They help Google reward you for your genuine SEO efforts, and stop search engines from missing vital content while they waste time crawling identical versions of the same information. You want your canonicalised URL to be the most authoritative version of the content, so there are some things you should never do:

• Never canonicalise a redirect page, as this can cause search engines to ignore or misinterpret your canonical tag. 
• Never use hreflang tags to point to non-canonical URLs, as this can also mislead Google. 
• Don’t apply canonical tags to the same or very similar pages, but instead pick one authoritative version. 
• Don’t use different canonicalisation signals across your website, but be consistent to avoid search engine crawler confusion. 
• Never set a canonicalised URL to ‘noindex’, as these are contradictory commands. While it is likely Google will go with your canonical tag over the ‘noindex’ tag, it’s not good practice to include both. 
• Do not use rel=”canonical” in the body of a webpage. It should only be used in the <head> section, and will be ignored if it’s not here.  

 Need an SEO expert to handle your canonical tagging?

If you’re still not quite sure what the best practice is for canonical tags, or how best to implement them, don’t panic! The fact is, even SEO experts take years to master the tricks and tools of the trade to implement this technical element of search engine optimisation, and it takes a lot of technical skill, know-how and regular spot checks and audits in order to make sure that your canonicalised URLs are correctly identified and are picked up by Google’s crawlers.  

At Online Marketing Gurus, we have nearly a decade of experience in crafting bespoke SEO strategies for businesses of all sizes and types. Whether you’re an eCommerce site struggling to win the day with an algorithm that’s confused by multiple parameterised URLs caused by filtering, or a website serving the same content on pages with different variants, we can help you get on top of your technical SEO with a consistent approach to canonical tagging that can help reestablish your authority in your industry.  

If you’re ready to turn the task of managing canonical tags over to a professional, our team of Gurus is here to help. Talk to us today about how our services can boost your rankings on Google and get you noticed by the right audience, at the right time.