Skip to main content

What Are Canonical Tags and Why are They Important?

Optimizing your website for search engines is essential if you want to improve your ranking in search engine results. Your website needs to be discoverable. Canonical tags help prevent duplicate content issues that can confuse search engines and keep your site from ranking.

What Are Canonical Tags?

Google, Bing and Yahoo! introduced canonical tags in 2009 as a tool for developers dealing with duplicate content on the website they created or managed. This tag appears in the <head></head> section of the HTML code and looks like this:

<link rel=”canonical” href=”” />

A canonical tag tells Google and other search engines which page on your website is the primary page — the one with the most complete and relevant content for keywords. Without the canonical tag, the crawler may choose the page it thinks is best or decide to give higher ranking to another website that is easier to decipher.

Benefits of Using Canonical Tags

  • Designate the page you want visitors to see in search results. For example, you may want to direct visitors to a page with a shorter URL that can be easier to remember.
  • Ensure that links from other sites all go to the same URL. When all of the sites linking to yours use the same URL, search engines can consolidate information into a single URL.
  • Simplify tracking metrics. Canonical tags can save you time when you’re monitoring SEO performance. Tracking the metrics of a single URL is easier than tracking the metrics of several URLs.
  • Manage syndicated content. You can send your preferred URL to other sites that want to link to your syndicated content. This gives you more control over the links that appear in search results for the content.
  • Improve the efficiency of search engine crawlers. Without a canonical tag, the crawlers may spend too much time sorting through all of your content instead of focusing on the newest — and ideally more relevant — content.

How Canonical Tags Help SEO

Using canonical tags boosts your site’s SEO because it simplifies the work of the search engine crawlers. Sorting through duplicate content takes time. The crawler has to determine which version of a page to index and rank. It also needs to decide whether it should consolidate or divide links.

The time the crawler spends reviewing duplicate content is time it could be spending finding new and more relevant content on your website. When you specify the primary page, you let the crawler do its job more efficiently. Your SEO improves, and your site can rank higher in search engine results.

Most Sites Have Duplicate Pages

Most sites — including yours — have duplicate content. This doesn’t mean you have duplicate pages for visitors to click through. Nor does it mean you have the same content listed on each page on your website. In fact, your visitors probably don’t even notice the duplicate content.

Duplicate content shows up on websites for a variety of reasons. A site may have one page that has several URLs linking to it. Sites that use session IDs to track visits can rack up a different URL for each session ID. User comment and printer-friendly page options can also create additional URLs that are essentially duplicate pages.

Canonical Tag vs. 301 Redirect

Canonical tags and redirects serve two different purposes. A 301 redirect lets the search engine know that you’ve permanently moved a webpage and no longer want it to be indexed. A canonical tag tells the search engine which page to crawl.

Situations when you may choose a redirect include the following:

  • You no longer offer a specific product or service.
  • You no longer want to update a specific page.
  • You removed a page from your site that visitors may still have stored in their shortcuts.
  • You moved a page to a new URL.

A canonical tag may be more beneficial in the following situations:

  • You have printer-friendly page options.
  • You have multiple pages from the same URL because products can be sorted.
  • You have products or services that fit in more than one category.
  • You have multiple pages using the same URL because of a paid search campaign you ran.

Best Practices for Using Canonical Tags

Canonical tags can solve the duplicate content problem, but it helps to know how to use them. Following these best practices ensures that you’re using these tags in a way that makes them useful for search engines.


Choose absolute URLs

According to Google’s John Mueller, you should use canonical tags on absolute URLs instead of relative URLs. Otherwise, the search engine may not identify the URL you want to tag. And that defeats the purpose of using a canonical tag.


Stick with lowercase letters in your URLs

URLs are case sensitive, so pay attention to the URLs you’re tagging. You can avoid duplicate content and make it easier for the search engine to do its job if you stick with lowercase letters in the URL. If you can’t do that, at least be consistent with your letter cases.


Double-check the domain version

Make sure the URLs you tag are the correct domain version for your site. If you use SSL, check to see that your URL has the https version instead of http. Otherwise, you risk creating duplicate pages.


Use self-referential canonical tags

Self-referencing canonical tags let you identify the correct version of the URL. They also lower the chance that the search engine will choose a different version of the URL. Although it’s not critical — and some may tell you not to worry about it get into the practice of using self-referential canonical tags.


Avoid tag packing on pages

You only need one canonical tag per page. Using more than one tag confuses the search engines. They will treat the page like one that does not have a canonical tag. Which means it may not rank as high as a page with only one tag.


Use canonical tags whenever possible

In the end, not using canonical tags is always worse than using them. People don’t want to see duplicate content on websites, and search engines want to give users the information they want. If the search engines don’t see canonical tags, they may skip the page, which can lower its ranking.

Understanding how to use canonical tags on your website is an important concept for SEO. Proper canonicalization can boost your site’s performance. Take the time to learn how to use canonical tags and implement them on your site. You may not be able to completely eliminate duplicate content, but you’ll help search engines navigate it.