How Do Canonical Tags Affect SEO

Canonical tags are a technical SEO feature that need to be used carefully. A snippet of HTML code within your website, they can give the search engine crawlers directions on whether the page is valuable to users and to you. So, let’s jump in, how do canonical tags affect your SEO?

A canonical tag tells the search engine which page is to be crawled and indexed, and therefore displayed in search engine results pages. They are useful to avoid duplicate content and prevent keyword cannibalisation. If used incorrectly, it can mean a page doesn’t get indexed or crawled at all. When used correctly they make your website crawlability better and more efficient.

Read on to learn more about canonical tags and how they affect SEO.

Why Are Canonical Tags Important?

Canonical tags are an important way of managing potential duplicate content. They highlight to the search engines which pages are the original, where you have pages with similar or the same content.

When using a canonical tag on a webpage, it is more likely that the search engines will display that page in search results above others on your site with similar content.

Without canonical tags search engine crawlers may:

Identify pages as duplicate content if they have very similar content.
Crawl and index lots of content that wasn’t necessary. If identified as duplicate this can harm your ranking potential. Learn more about how search engines crawl and index pages.
Index the wrong pages – If you don’t use canonical tags to tell the search engines which page holds the most value, they may select a page that isn’t the most helpful to your users.

What Are the Benefits of Canonical Links for SEO?

There are many benefits to SEO if you correctly implement canonical tags to your pages where they are needed.

Search engines know which pages to crawl and index. Meaning pages they display to users have the most potential to rank on the search engine results pages, and are the ones most beneficial to your users from your website.
Link equity won’t be shared across multiple pages – if you have multiple pages that are similar and are interchangeably displayed for a query, a canonical tag can help to ensure that all link equity goes to one page rather than spread across multiple pages.
Your crawl budget won’t be wasted on pages that are not as important and your pages with the most important content have a higher chance of being indexed.
You have a way of controlling your content so it isn’t flagged by crawlers or on audits as duplicate. Duplicate content is tricky, but Google values unique, high-quality content as part of E-E-A-T, so the more original and useful to the user, the better. Learn more about content audits and when it’s time to review them.

When to Use Canonical Tags

Canonical tags should be used when:

You want to avoid pages being flagged as duplicate content – duplicate content can lessen the value of your site, potentially cause keyword cannibalisation and dilute link equity.
Content is shared across websites – for example, if you have an article that someone wants to use on another website. To make sure the search engines know yours is the original version and so your page appears in search results in favour of theirs.

It’s important not to confuse using a canonical tag for instances where there may be a more appropriate action such as:

Using a redirect – If you have a webpage that is being removed, whether through redesign or updating the content and URL, you will want to create a redirect not a canonical.

A canonical will only tell search engines which is the preferred page and means both are still accessible to users, whereas a redirect sends the user automatically from the old page to the new. We have a dedicated blog post to redirect mapping if you’d like to learn more.

TIP: Make sure when linking to pages internally on your website that you use the preferred canonicalised URL. This avoids confusing the search engines and shows them which page you want to be indexed.

Should Every Page Have a Canonical Tag?

Although not specified as a must in Google’s guidelines on canonicalisation, we would recommend using them on every page to give stronger signals to the search engines about which pages are of importance on your website.

It is important to also ensure that your sitemap also only includes canonicalised pages. This is so:

The search engine doesn’t crawl unnecessary pages.
Used alongside canonicals it further displays to the search engines that this is the page they should index and display on the results pages.

To learn more about sitemaps read our dedicated blog on sitemaps and how often you should submit one.

How Do I Know If a Page Has a Canonical Tag?

To check if a page has a canonical tag:

Right click on your page – Click ‘View page source’
On Windows press ‘CTRL + F’ and search for ‘canonical’
In the source code you will see ‘<link rel=”canonical” href= ‘ This is then followed by the URL that has been set as the canonical page.
Ensure that there is only one canonical per page, as if there are multiple, it is likely they will get ignored altogether. See Google’s guide on common canonical mistakes.

Get Help With Technical SEO

Canonicals can be tricky to use and if used incorrectly can be costly to your rankings. We have only scratched the surface of the complexities of canonicals and best practices for using them in this blog. However, if you’re looking for help implementing Technical SEO, you’re in the right place.

Wildcat Digital is a dedicated digital agency with specialists in Technical SEO that can assist you with getting your strategy right. If you’d like to improve your visibility online, get in touch with us today.