Canonical tags, often referred to as rel canonical, are a HTML element on your website that you can use to let search engines know which is the main version of a page. They are helpful because they can reduce issues of duplicate content.
Duplicate content can be a problem on large websites, especially eCommerce sites, as results are filtered down so that the user can find the exact product they are looking for.
How to Implement Canonical Tags
A canonical tag should only be present in the <head> section of your website. You should only include one canonical tag per page; otherwise, you will be sending conflicting signals to search engines.
How your canonicals are implemented will vary per website and how it is built, but remember your canonical tag will only be valid as a <link>. For example, if you use Yoast on a WordPress website, you can add canonicals through the Advanced section on each page. You can use other various plugins to do this too, and the same applies to other CMS’, but if it is possible to add your canonical tags directly into the code, this would be the preferred option. This way, if the plugins were to be removed or encountered another issue, then your canonicals would still be in place.
Do Canonical Tags Affect SEO?
In short, yes. The use of canonical tags can impact your SEO rankings both positively and negatively. This is because you are telling search engines which version of the page you would like them to include. For this reason, it is important that you use them carefully and that you understand how they can affect you.
SEOs can also use them to point from HTTP to HTTPS versions, and the same goes for www and non-www versions of a website (depending on which is used).
Rel canonicals can help your website by reducing cannibalisation and bloat and emphasising the importance of specific pages.
However, they can also hurt your website if not used correctly by noindexing pages in favour of another.
In general, self-referencing canonicals should be used. Self-referencing means the canonical is pointing back to itself, but there are some instances where it would make sense to point to other URLs.
Canonical Tag Recommendations
The following rules should help you in your canonical tag implementation:
Canonical tags should use an absolute URL with the HTTPS protocol.
E.g. a homepage’s canonical tag should look like this:
The canonical tag should be self-referencing.
E.g. this URL’s canonical tag – https://www.mymanchesterwebsite.com/where-to-stay/city-centre
Canonical tags on pagination pages should be self-referencing unless the pagination contains query strings.
When the pagination contains query strings, then you should strip out the query strings, and the canonical tag should point to the pagination:
E.g. the URL’s canonical tag – https://www.mymanchesterwebsite.com/things-to-do/entertainment?page=2
However, the canonical tag for this URL, for example:
URLs containing query strings should have a canonical tag to the clean URL.
E.g. this URL’s canonical tag – https://www.mymanchesterwebsite.com/where-to-stay/serviced-apartments?sort=PriceLow
The canonical tag for this URL, for example: https://www.mymanchesterwebsite.com/food-and-drink?totalpages=8&page=4
Should point to the clean URL:
As with everything in SEO, nothing is set in stone, and it often “depends” on the content itself. Before implementing anything on your website, always take the time to understand how the actions could affect your performance. If you are unsure, try checking with colleagues or others in the industry before implementing anything.
I hope you find the above rules helpful and can use them on your own website when adding canonicals.