A canonical tag is a small HTML code that helps search engines understand the page’s main version. This code separated the page from its duplicates and similar pages. If you have different pages with similar content, you can use the canonical tag to specify which page is the main version and which ones must be indexed. 

The canonical meta tag tells the search engines that the enclosed URL is the original and definitive version of the page. The canonicalized URL looks like this: <link rel=”canonical” href=”https://www.example.com”>. To summarize, the canonical tag tells Google which page you want to appear in the search results.

Why is a canonical tag important for SEO?

The primary objective of a canonical tag is to help search engines differentiate original versions of a page from its duplicate pages. With pages looking alike, it becomes difficult for Google to decide which page has to be indexed and which one has to be ranked. This will eventually affect the rankings of those pages that have been curated carefully to land in search results. 

Aside from the fundamental purpose of a canonical tag, its other significant benefits are:

1. Canonical tags consolidate PageRank

Canonical tags consolidate link equity(PageRank) from duplicate pages into one central page. Duplicate pages quickly get many backlinks from external sources such as social media, random websites, and more. These pages eventually remove the link equity from the main page, disabling it from ranking and appearing in the search result. 

With the help of a canonical tag, you can keep the link equity intact for the original page. The PageRank can be transferred into a single URL and improve the page’s overall ranking on Google.

2. Canonical tags manage syndicated content

Canonical tags help the search engine decipher which website contains the original content and which has syndicated content. In addition, many website owners publish content on other websites, mainly for promotional purposes. 

Syndicated content makes it all the more tricky for Google to decide on the source of the content. But, a canonical tag helps in resolving this problem by promoting the correct version of the page on Google search.

3. Canonical tags improve crawling

Canonical tags help search engines crawl to pages that want to be crawled or indexed, as opposed to those that don’t intend to. Duplicate pages will only waste Google’s resources and time if they are not created for crawling or indexing purposes. With the help of a canonical tag, Google can focus on those pages that matter and save theircrawl” budget.

What are the best practices to apply for a canonical tag?

Canonical tags are easy to implement. However, one should follow the rules discussed below to make them successful.

1. Use self-referencing canonical meta tag

Even though it is not mandatory, adding a canonical tag to a page that points to itself are good. Self-referencing canonicals will help search engines be clear about the canonical versions of a page. Most ‘(CMS)’ of today add self-referencing URLs automatically, but you will have to come up with your own if you use a custom CMS.

2. Use absolute URLs

There are two purposes for using absolute URLs for canonical tags, and they are:

  • To avoid unintentional mistakes
  • To prohibit the bad interpretation of canonical URLs by search engines compared to relative URLs.

3. Use lowercase URLs

Uppercase and lowercase URLs can have an impact on search engines. However, lowercase URLs will help canonical URLs maintain consistency and avoid duplication in search engines. Therefore, you could practice implementing lowercase URLs to both your servers and the canonical tags.

4. Use the correct domain version

If you are using SSL, ensure that you do not implement any non-SSL URLs in your canonical tags. If you do, you could be responsible for confused and unexpected results. Therefore, always keep an eye out for the domain version, be it HTTP or HTTPS.

5. Canonicalize cross-domain duplicates

Canonical tags can reference your main pages from other domains, not just from within your website. If you have duplicate content on particular pages of different websites, make sure to:

  • Use self-referencing canonical tags on the original page
  • Apply the canonical tag on the external page that references the original one.

What practices to avoid while using a canonical tag?

The following practices should be avoided while applying canonical tags:

1. Multiple canonicals on one page

Look out for multiple canonical tags that may be present in the HTML of a page. This is because having numerous canonical tags on one page will cause search engine confusion and result in poor website performance.

2. Avoid canonical on non-duplicates

It is a must that the content on the original page and the duplicate content on other pages should be at least similar, if not identical. Implementing canonical tags on pages different from each other will confuse the search engine and be ignored by them.

3. Canonicals on paginated pages

Paginated pages have fragmented content spread over multiple pages. Since the tag on page 1 is not equivalent to the one on page 2, the canonical tag would be considered incorrect. Therefore, it is better to use self-referencing canonical tags on every individual page.

4. Don’t block canonicals via robots.txt

One should never block URLs with canonicals using a robots.txt file, as it restricts Google from crawling to the duplicate pages. In addition, this will disable the search engine from seeing canonical tag references to the main page. Even the PageRank will not be transferred to the main version if the URLs and canonical tags are blocked.

5. Don’t use canonical tags in the body

Canonical tags should always be applied to the head section of your pages and not in any other place of the HTML document. This is because Google will undoubtedly ignore the canonical tags specified in other areas besides the head section.

6. Avoid canonical loops and chains

It is always better to use canonicals that make references directly to the main page to avoid canonical loops.

Summarising a canonical tag

Canonical tags are not complicated. However, they must be implemented correctly to get the ball rolling on the content on your websites. As they act as signals to search engines, it is good to use proper canonical tags and regularly audit your website for the same.