Sean Butcher is Head of SEO at BlueArray. As part of the afternoon session of Crawl & Indexation at BrightonSEO, Sean Butcher continues the session by focusing on canonical tags with his talk, “So You Think You Know Canonical Tags?”.
To kick things off, Sean starts by defining the the canonical tag and its benefit for SEO.
About the canonical tag
If your website generates and displays the same (or very similar) content on multiple URLs, a canonical tag can be used to bucket all duplicate URLs into a master URL, a.k.a. the canonical version. The main application of canonical tags, therefore, is to reduce duplicate content across your site. You can use canonical tags to consolidate several different URLs configurations, from trailing slash and query parameters to non-www and parallel URLs for mobile.
While there are other options to reduce duplicate content across a site, such 301 redirects, noindex meta tags and parameter exclusions through Search Console, why should we choose the canonical tag as SEOs? Sean named three specific reasons:
- Easier on development resource
Canonical tags are relatively easy to set-up, even as non-technical SEOs or developers. Most CMSs support even support them, like WordPress through their Yoast plugin. - 301 redirects increases pressure on the server
Several redirects at once can put unnecessary pressure on your server and as such, can reduce page speed. - Make other versions accessible for user experience
While duplicate content is usually unknowingly present on a site, sometimes it may deliberately present for usability reasons.
It’s at this juncture that Sean Butcher recommended watching Moz’s Dr Pete’s Whiteboard Friday on the difference between 301s, 302s and canonical tags.
Things to consider
To implement canonical tags correctly onto your site, Sean recommended the following are put into place:
- Make sure your canonical version is the canonical, not a 404/301/302
- Use absolute URLs when assembling the canonical, not relative URLs
- Internally linking around your website must utilise to the canonical tag
- The canonical URL needs to be the version listed in your XML sitemap
Canonical tags are related to indexation, not crawling as hinted at by John Mueller back in 2016. While they’re not likely to save on crawl budget, they’re more there to reveal to search engines which URLs are duplicated and which are the master versions.
@bheligman probably not (or not much). we have to pick a canonical & have to crawl the dups to see that they’re dups anyway.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) November 30, 2016
Found in the <head> section of a web page, the canonical tag should only be used to consolidate highly similar content.
Canonical tags are also a hint, not a directive. While they’re a very strong hint, they still may be ignored in favour of other signals. As webmasters, you also need to ensure only one canonical tag is present on each web page.
Alternative methods
While canonical tags are predominantly used within web pages, Sean also revealed some other use cases for the tags:
- Other assets
Canonical tags can be used to consolidate duplicate content across PDFs, for example, on printer-friendly versions of your content. In addition to this, you can also use them on images, perhaps as a means to redirect link equity through to relevant pages. Canonical tags such as these can be inserted via your site’s htacess file or via your HTTP header. - Paginated series
Another alternative method of canonical tag usage is to consolidate duplicate content across a paginated series. While pointing ordinary canonical tags to “page 1” of your paginated content is not advised, Sean recommends how your efforts are better focused in creating a “View all” page, or by using the rel=”next” or rel=”prev” tag (in conjunction with self-referential canonical tags and markup, if necessary). - Cross-domain canonicals
Cross-domain canonicals can be used to consolidate link equity and duplicate content across individual domains. This is especially useful if you know your content strategy to involve syndication and the licensing of content. In this instance, you can use cross-domain canonicals to reference the originator of the content (a concept I have written about in a previous blog post of mine).
For more about Sean’s presentation, you can view his slides here where he discusses several canonical tag case studies in greater depth.
