1. Glossary
  2. Crawlers
  3. Rel Canonical Tag

Rel Canonical Tag

Rel=canonical element, or the canonical link

A rel=canonical tag is a snippet of HTML code which marks up web pages that are at risk of being interpreted as duplicate content. By implementing this tag in pages with similar or identical content, webmasters are able to convey to search engines which is the original page—the ‘canonical link’—and which are subsequent copies. The canonical link, established as the preferred version, is given ranking priority over the copies, thus avoiding duplicate content issues.

In SEO, content is king. Generating new, fresh, relevant content for your blog or website should be at the heart of your digital marketing strategy. However, every now and then, a website can find itself needing to use the exact same content more than once across their site, or even across multiple sites.

Google and other search engines will consider this duplicate content. But for many businesses some duplication is inevitable, for instance when there are only subtle variations on a product or when press releases are published identically across different platforms.

Most duplicate content, Google understands, isn’t a result of webmasters trying to manipulate search results. In 2013, Google spokesman Matt Cutts stated that there is no penalty for duplicate content, but that it can be detrimental to your website’s position on search results pages.

In order to avoid this, you need to make it absolutely clear to search engines which URL is the original version of content—the one you value the most—and which are the subsequent copies. Your SEO agency will be able to spot potential duplication issues and help you to identify which pages should be marked as copies, and which as the original.

This is where rel=canonical comes into play.

Put simply, the rel=canonical tag is a way of labelling your content for search engines. It’s a line of HTML code which, when placed correctly on a page with duplicate copy, tells the search engine to give all SEO credit to the original version.

In this way, website curators are able to channel all the link metrics, such as backlinks and page authority, into the original, rather than diluting it across multiple pages and causing internal competition. This original page will, therefore, rank highest in search so you should make sure you are selecting the best, most valuable version to mark as canonical.

Website structure and user navigation can also put website curators in a position where duplicate content is necessary. We see this issue occur most often on e-commerce sites like Shopify where a single product may have several different URLs depending on how the user reached the product page through the site.

For instance:

Route & URL 1: http://www.example.co.uk/gift-ideas/men/product/
Route & URL 2: http://www.example.co.uk/applicances/product

Here’s an example of how the rel=canonical tag would appear in the header of a duplicate page:

<link rel=“canonical” href=”http://www.example.co.uk/preferred-version/” />

The link included in the code is the URL location of the original copy, it is the canonical link.

Choosing the canonical link

The content you choose to mark as the original should be the version you value most. There are a number of factors which could influence your decision, such as the appearance of the page and the tidiness of the URL. A shorter URL, such as Route & URL in the above example, is often preferable.

If there are no obvious differentiating factors, then your marketing or SEO agency should be able to identify which page is attracting the highest volume of traffic or ranking best in search. They would then suggest adding a canonical tag to this page for maximum SEO benefits.

SEO and canonical links

A rel=canonical isn’t a mandatory search engine requirement, but from an SEO perspective it’s hugely important. While you are unlikely to be penalised for duplicate content, if crawlers don’t know which page to show in search then they may show the wrong one, or neither. This could affect your overall site visibility and traffic. If you have duplicate content, then remove it, control or change it.