You’ve probably invested a lot of time and energy into your websites’ Search Engine Optimization (SEO) because you want your content to rank well in Google. You’ve wrapped your head around on-page SEO concepts like headings and meta descriptions . You’ve learned about backlinks and link-building. You’re even cranking out high-quality content on the regular. But everything you’ve learned and everything you’ve done could be jeopardized if you ignore canonicalization.
Understanding how to use canonical tags and set canonical URLs is essential for optimizing your site for search. While canonicalization isn’t a tough concept to master, simple implementation errors can cause widespread issues that could negatively affect your website’s performance.
Let’s start with the canonical tag definition.
What Are Canonical Tags & Canonical URLs?
A canonical tag is an HTML element that tells search engines that a specific URL is the main version of a pag
What Are Canonical Tags & Canonical URLs?
A canonical tag is an HTML element that tells search engines that a specific URL is the main version of a page, and it’s the one you want to appear in search results. It’s especially useful when you have pages with very similar (or the same) content and want to ensure that search engines don’t categorize them as duplicate content .
What’s the Difference Between Canonical Tags & Canonical URLs?
You might hear people use the terms “canonical tags” and “canonical URLs” (or “canonical links”) interchangeably, which is inaccurate and can cause some confusion.
Before getting down to the difference between the two, let’s define each.
What Is a Canonical Tag?
A canonical tag (also known as “rel canonical”) tells search engines that a particular URL is the master copy of a web page. Using a canonical tag tells search engines which version of a page you want to appear in search results.
Canonical tags are found along with other metadata in the head () of a page’s HTML code. They look like this:
A canonical tag can be self-referencing — meaning that it points to its own URL — or it can point to another page’s URL to consolidate signals to search engines. (More on why you want to avoid mixed signals below.)
For example, if you repurpose a blog article and post it on Medium , you’ll want to specify that the post on your website is the canonical version and should be the one that appears in SERPs.
What Is a Canonical URL?
A canonical URL (also known as a canonical link) is the primary URL for a set of duplicate pages.
“A canonical URL is the URL of the page that Google thinks is most representative from a set of duplicate pages on your site.”
For instance, in the example below, the canonical URL is specified inside the canonical tag .
The canonical URL dictates which page to show in the search results.
Why Canonical URLs Matter for SEO
By specifying a canonical URL, you’re telling search engines which preferred version of a page to display on search engine result pages (SERPs), so you can present the URL that makes the most sense to show someone accessing your site organically.
For example: if I am searching for red shoes, I wouldn’t want to click through a result in the search results and be taken to a page showing red shoes in a random size.
I would want a URL that doesn’t assume my shoe size but still presents me with the same product page from a functional perspective.
Consolidate Link Signals
When you have duplicate or similar pages on your site, it’s possible that individual URLs could earn links from external sources.
When you use canonical URLs to consolidate the link signals from multiple pages into a single URL, you’ll improve the ranking of that one page — increasing the likelihood of pushing your content up in search results.
Managing Syndicated Content
It’s a common marketing tactic to place content across different websites to increase awareness among new audiences. If that syndicated content is similar enough to content on one of your pages, search engines might be confused about which page to return correctly for relevant search queries. To make sure your original piece of content is the one that ranks, you’ll want to use canonical URLs to signal that your page is the primary piece of content to return for search. The best practice is to use a self-referential canonical tag on your article and to have the syndicated content specify you as the canonical version with a cross-domain canonical tag.
Don’t Let Googlebot Crawl Duplicate Pages
If you have a large website with a lot of pages, canonical URLs will help crawl bots prioritize your new pages instead of crawling duplicate versions of the same page. Without canonical URLs, index bloat could exhaust your crawl budget , decrease your domain’s organic quality, and potentially lower the ranking of your other pages. If you have a large amount of duplicate pages, use robots.txt to prevent crawling.
Reasons Why Duplicate Content Exists
Sometimes it makes sense to intentionally create “ appreciably similar ” pages because they serve different purposes. For instance, if you have customers in both Canada and the U.S., you might create two product pages that are nearly identical except for the prices (to account for the US/CAD exchange rate). In this case, you’d implement canonical tags on these pages, along with hreflang tags to tell search engines which page to serve to which searcher based on their location.
In addition, content management systems and dynamic websites can create duplicate content that you’re not even aware of. Some sites add tags automatically, allow multiple paths to the same content, and add URL parameters for searches, sorts, or currencies. It’s possible to have thousands of duplicate URLs on your site and not even realize it.
For instance, these multiple URLs might all display the same content:
But to a search engine, this isn’t just one page of content. It’s eight pages of duplicate content . Fortunately, canonical URLs help search engines identify different variations of a page as a single URL and prevent duplicate content issues.
Using 301 Redirects to Specify Canonical URLs
According to Google , you can use 301 redirects to tell Googlebot that a redirected URL is a better version than another URL. With one major caveat — you should only use a 301 redirect for a duplicate page that you plan to retire.
That being said, 301 redirects can be the best way to clean up duplicate content caused by:
HTTP and HTTPS
http://mywebsite.com/redshoes/ vs. https://mywebsite.com/redshoes/
Non-WWW and WWW
https://mywebsite.com/redshoes/ vs. https://www.mywebsite.com/redshoes/
Trailing-slash and non-trailing slash
https://mywebsite.com/redshoes/ vs. https://mywebsite.com/redshoes
When it comes to individual pages, rather than groups like those mentioned above, your best bet is to use canonical tags.
How To Implement the Canonical Link Element
Let’s say you have two pages with duplicate content and that you want to keep both on your website. To ensure the one you want to appear in search results is considered the canonical page, you’ll need to add a rel canonical tag to the page you don’t want to appear in search results.
If I had the following two pages on my site with duplicate content, and I wanted to set the first one as canonical, I would need to add a canonical tag in the header of the second page pointing to the first URL.
The tag would look like:
If you’re using WordPress for your website, you can easily add canonical tags with the free version of Yoast.
Simply go to the post or page you’d like to add a tag to and open the Yoast sidebar on the right-hand side. The following will appear:
Enter the canonical URL (including https or www if it’s part of your absolute URL) in the bottom box under the “Advanced” menu. No need to add an HTML tag — just paste the URL.
How to Create a Self-Referencing Canonical Tag
To make sure that my first link-building page is considered canonical, I might also add a self-referencing canonical tag to its header.
The canonical tag and canonical URL would be the same as the example I just walked through, but instead of pasting the tag on a different page, I would be pasting into the header of the canonical page.
If you use hreflang, I recommend using self-referencing canonical tags on the different language versions of your homepage.
Canonical Tag Best Practices
Now that you know the answer to the question, “what are canonical tags”, it’s time to put our knowledge into practical use.
Canonicals are easy to implement. Once you understand some best-practices, you’ll find that locating and cleaning up duplicate content becomes much more manageable.
1. Use self-referential canonical tags.
In the case where you have a primary page and three duplicates, you can go ahead and place the canonical tag on all of them, even if the one on the primary page is pointing to itself.
As a matter of fact, even when you don’t have any duplicate pages, Google recommends using self-referential canonical tags as a best practice. The reason? There might be links to your pages that contain URL parameters and UTM tags , which Google could pick up as the canonical version. It’s not critical to use self-referencing canonical tags, but it’s a good insurance policy.
2. Canonicalize your homepage.
Not only are homepage duplicates common, but people might link to your homepage in ways you can’t control — using parameters or UTM tags. It helps to be proactive and put a canonical tag on your homepage template — just to be safe.
3. Don’t send mixed signals.
While adding canonical tags to your pages is a straightforward process, you do need to be careful not to send mixed signals to search engines by mixing canonical tags with redirects or canonicalizing two pages to each other.
- If you canonicalize http: //mywebsite.com/redshoes/ to https ://mywebsite.com/redshoes/
- don’t redirect https ://mywebsite.com/redshoes/ to http: //mywebsite.com/redshoes/
- If you canonicalize http: //mywebsite.com/redshoes/ to https ://mywebsite.com/redshoes/
- don’t canonicalize https ://mywebsite.com/redshoes/ to http: //mywebsite.com/redshoes/
And, don’t chain canonical tags. For example:
- Don’t canonicalize http: //mywebsite.com/redshoes/ to https ://mywebsite.com/redshoes/
- then canonicalize https ://mywebsite.com /redshoes/ to https ://mywebsite.com /red-shoes/
Mixed signals make it hard for search engines to choose the right page to return for search results. Without clear signals, search engines might make bad choices.
4. Only use canonical URLs in sitemaps
Be careful not to include non-canonical URLs in your sitemap . Google assumes that URLs included in a sitemap are the canonical versions of your pages.
5. Use absolute URLS to avoid errors
An absolute URL includes the entire URL for a website, including its protocol and domain. If I wanted to set our Link Building Services page as a canonical page, I’d want to use the absolute URL:
A relative URL does not include the protocol and domain name. It only includes the “path,” which in this case would be “/services/link-building.” Leaving out the protocol ( HTTP or HTTPS ) will also result in search engines viewing your URL as a relative URL and not an absolute URL, which could result in it recognizing the wrong page as the primary version.
If you always use the absolute URL for your canonical link, then you can avoid potential errors caused by only using a relative URL.
6. Point to pages in the same language
If you’re using hreflang and have similar web pages in more than one language, be sure that when you use a canonical tag, you point to a URL in the same language. So if you have German and English web pages tagged with the appropriate hreflang tags, and you want to add a canonical tag to a German page, it should link to another German page, not an English page.
How to Find & Fix Rel Canonical Problems
Since sending clear signals to search engines makes it easier for people to find your website, it’s important to run regular audits to find and fix any issues related to canonical tags.
Recommended Tools for Site Audits
These paid site audit tools will highlight any canonical errors they find on your site so you can address them appropriately.
Common Canonical SEO Problems & How to Solve Them
Here are a few rel canonical problems that might come up when running a site, audit along with some simple fixes.
1 – No redirect or canonical to HTTPS homepage from HTTP version
If users can access both HTTPS and HTTP versions of your website, your site audit will flag this as a duplicate content issue.
Fix this by implementing a 301 redirect to the correct version or add a canonical tag that references the HTTPS version on the HTTP pages.
2 – Pages with broken canonical links
If your pages have broken canonical links, crawl bots can’t understand them as canonical URLs. This error might mean that your canonical links point to non-existent pages, making it difficult to index your content.
Fix this by updating these to point to the correct canonical URLs.
3 – Pages have multiple canonical URLs
If you have more than one canonical URL on a page, Googlebot won’t know which way to go to find your primary content.
All you need to do to fix this is remove the duplicate tags, leaving the correct one in place.
“What Are Canonical Tags?” In a Nutshell
Although “canonicalization” is tough to say, it’s not tough to understand. Using canonical tags is a foundational (although often overlooked) part of technical SEO strategy. While it requires some organization and consistent maintenance, there’s no reason to leave this stone unturned while you seek to maximize organic traffic for your business.
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