On December 15, 2009, Google, Yahoo! and Bing presented the canonical label (html or rel=”canonical”) to fight against duplicate, copied or very similar content, but… do you know what it is for?
What is the canonical tag for in SEO
The vast majority of websites have two exactly the same websites, one with all three www and one without:
- https://www.mydomain.com/
- https://mydomain.com/
With the canonical tag, sites can tell search engines what is the original or preferred URL, so that it is the one that they prioritize and give it relevance and which are the URLs to ignore. That is, the canonicalization allows us to choose the best URL to display our website.
How to use the “canonical” tag
In any eCommerce or in sites where content is managed, it is normal for several URLs to direct us to the same content, so logically, it is duplicated. No one better than Google to tell us how to use the canonical tag without errors.
In principle, it is worth adding to the websites, within the , a tag such as: .
In order not to make it difficult for search engine robots whenever there is duplicate content, Google recommends that we:
- Consolidate liaison callsigns. It is advantageous to allow search engines to consolidate the information available for each URL (such as links to them) into a single preferred URL.
- Monitor metrics for a single product or topic. By having multiple URLs, it is more difficult to obtain consolidated metrics for a specific article.
- Determine the URL that users should see.
- Manage syndicated content. If you distribute your content to be published on other domains, it is recommended that you consolidate the ranking of the page with your preferred URL.
To assign a canonical URL it is recommended:
- Set the preferred domain. The preferred domain or canonical domain is the one that we want the search engines to index. Links can lead to your site using the www or non-www versions of the URL.
- Indicate the preferred URL with the rel=”canonical” link element. Mark the canonical page and any other variants with a rel=”canonical” link element. Add a element with the rel=”canonical” attribute to the section of these pages.
- Use a sitemap to set preferred URLs for the same content. A sitemap is a file in which the pages of your website can be listed to inform Google and other search engines about the organization of the content on your website. Search engine web crawlers, for example Googlebot, read this file to more intelligently crawl the site.
- Use for non-canonical URLs. A 301 redirect on the server is the best way to ensure that users and search engines land on the correct page. Status code 301 means that a page has been permanently moved to a new location.
- Indicate how to manage dynamic parameters. Use parameter organization to tell Google which parameters you want to be ignored. By ignoring certain parameters, you reduce duplicate content in the index and make it easier for Google to crawl your site.
- Specify a canonical link in the HTTP header. If you can configure your server, you can use rel=”canonical” HTTP headers to indicate the canonical URL of HTML documents and other files, such as PDF files.
- Prefer HTTPS over HTTP for canonical links. Google prefers HTTPS pages over the equivalent HTTP pages as canonical, except where there are conflicting flags such as the following:
-
- The HTTPS page has an invalid SSL certificate.
- The HTTPS page contains insecure dependencies.
- The HTTPS page is robotized (and the HTTP page is not).
- The HTTPS page redirects users to or through an HTTP page.
- The HTTPS page has a rel=”canonical” link to the HTTP page.
- The HTTPS page contains a noindex robots meta tag.
-
Configuration errors when using the tag
the following practices for the use of rel=canonical:
- A large part of the content of the page must be present in the canonical version.
- Check that the target URL of the rel = canonical exists (not an error or “404 soft”).
- Verify that the target of the rel=canonical does not contain a noindex meta tag.
- Making sure you prefer the rel=canonical URL to show up in search results (instead of the duplicate URL).
- Include the rel=canonical link in the page header or HTTP header.
- Make sure there is no more than one rel=canonical for each page. When there is more than one rel=canonical, all rel=canonical will be ignored.
In conclusion, Google proposes:
- Check that most of the main text content on the duplicate page also appears on the canonical page.
- Check that the rel = canonical is only specified once and is in the of the page.
- Check that the rel=canonical points to an existing URL with good content (i.e. not a 404, or worse, a “soft” 404).
- Avoid using rel=canonical on landing pages or categories with featured articles as it will make the featured article the preferred URL in search results.
If you have a version for each device, for example, mobile and computer, you should clearly indicate what the canonical URL is so that Google or another search engine does not select it for you.
Jose Luis Blanco Cedrún, professor of the Master in Web Analytics and Big Data, of
Image: Depositphotos
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