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The Top 10 Questions About Canonical Tags Answered

13th June 2019Will LauWill Lau

Canonical tags tell search engines which version of a page is the primary or master version. For example, if a website has two or more versions of a single page, adding a canonical tag tells Google what version should be indexed and what versions are duplicates.

Seems simple enough! But when it comes down to the implementation, things can get a little tricky. That’s why we’ve compiled a list of answers to the top 10 most common questions we get about canonical tags.

1. Do canonical tags pass PageRank?

Yes, canonical tags pass PageRank!

According to Google:

“You should choose a canonical URL to consolidate link signals for similar or duplicate pages. This helps search engines to be able to consolidate the information they have for the individual URL (such as links to them) into a single, preferred URL. This means that links from other sites to http://example.com/dresses/cocktail?gclid=ABCD get consolidated with links to https://www.example.com/dresses/green/greendress.html”

In other words, links to page B will be counted as links to page A if page B canonicals to page A.

It is ultimately up to Google to decide how your URLs will be treated, but generally, when Google respects your canonical tags, PageRank will be passed.

2. Are self-referencing canonical tags a good idea?

Yes, it’s normally considered best practice to add a self-referencing canonical tag. A self-referencing canonical tag, like it sounds, is one that canonicals to itself. This ensures that multiple versions of the page (duplicates) don’t get indexed separately.

For example, the page https://www.example.com would have a rel="canonical" tag that points to https://www.example.com (the same URL). This would prevent alternate versions of the same page such as https://example.com from getting indexed.

It’s also OK to not have a self-referencing canonical tag. Just keep in mind that Google will then choose one URL as the canonical and it may not be the version you prefer.

3. Is there any benefit to absolute vs. relative URLs in canonical tags?

Absolute canonical tags are typically preferred because they provide a more concrete signal as to which URL is preferred. Absolute URLs are links to the full URL, root domain and all. Relative URLs list the URL path only.

For example:

  • Absolute URL: https://example.com/page/one
  • Relative URL: /page/one

Canonical tags that use relative URLs can mistakenly be placed on subdomains and other domains that aren’t necessarily canonical version.

For example, if instead of listing the full URL in your canonical tags (<link rel="canonical" href="https://example.com/page/one" />) you list a relative URL (<link rel="canonical" href="/page/one" />) and a staging site gets indexed accidentally, both sites would be claiming to be the canonical version. These conflicting signals could result in Google treating a non-preferred version of the page as the canonical.

4. Why is Google ignoring my canonical tag?

Canonical tags are suggestions, Google can easily ignore them.

If you’ve asked this question before, it’s likely that you received a “Google chose different canonical than user” message in Google Search Console.

When Google picks a different canonical than the one you declared, it means they don’t trust the tag’s accuracy. In many cases, Google will choose to ignore your canonical tag if the content between the two versions of the page are not similar.

The canonical tag is supposed to be reserved for duplicate or very similar pages. If Google detects that the declared canonical version of a page is actually quite different from the pages you declared its duplicates, then they will likely ignore the tag and index both separately.

Also, linking to the non-canonical version of your page can send confusing signals to Google as to your preference. So, if you want Google to respect your canonical, another good measure is to link consistently to the URL you consider to be the canonical.

You can use the URL inspection tool to learn which page Google considers canonical.

5. Are canonical tags weaker than 301 redirects?

Whereas canonical tags are suggestions, 301 redirects are more definitive. Permanent 301 redirects tell Google “this page has permanently moved.”

Even though canonical tags are “weaker” signals than 301 redirects, they are often the preferred method for handling duplicate content. A prime example of this is duplicate content that has to remain on the site for some reason. If deleting and redirecting is not an option, then a canonical tag to the primary version of the page should work well.

6. Are canonical tags only for exact page duplicates or can they be used for similar content too?

Canonical tags should be reserved for duplicates or near duplicate pages. If you canonicalize a URL to a page that’s too dissimilar, Google may ignore your canonical.

If you have a single piece of content that is accessible by multiple URLs, a canonical is appropriate. If you wouldn’t consider it the same or nearly the same content, then a canonical may not be appropriate.

7. What types of pages should you canonicalize to a different URL?

The most common examples of pages requiring canonical tags that we find is parameterized URLs, either for sorting/filtering or for tracking IDs.

Google list multiple examples of what constitutes duplicate or near duplicate content, such as:

  • Multiple versions of a page to support different device types. For example, https://example.com/news/ and https://amp.example.com/news/.
  • Parameters and session IDs. For example, https://www.example.com/products?category=dresses&color=green or https://example.com/dresses/cocktail?gclid=ABCD
  • A single page living under multiple category subfolders. For example, https://example.com/decor/pillows and https://example.com/bedroom/pillows
  • Having a server that’s configured to serve the same content for www/non-www and http/https variants. For example, http://example.com/green-dresses and https://example.com/green-dresses
  • Syndicated content. For example, the same article published on multiple news sites.

Yes and no. While it’s a good idea to send consistent signals to Google about which version of your page is preferred, and linking to the canonical version is part of that, sometimes there’s just no way around linking to a non-canonical URL.

It’s a good idea to periodically find pages on your website that link to non-canonical URLs and clean up any that aren’t necessary. Google says that they crawl non-canonical URLs less often, but if you keep linking to those pages, Google will still crawl them quite often. To preserve your crawl budget, it’s important to clean up any unnecessary links to non-canonical URLs.

9. What are some of the biggest mistakes people make with canonical tags?

One of the biggest mistakes we see when it comes to canonical tags is believing that they don’t waste crawl budget. Google says that they will crawl the non-canonical version of your pages less often, but they still get crawled, and even quite often when those URLs are linked to.

In the example below, you can see how often these URLs are being crawled by Google even though they are not the canonical version of the page.

URLs Explorer - 1

We also tend to see a lot of canonical tags that point to dissimilar content. Canonical tags are supposed to be reserved for duplicates, but many websites have canonical tags pointing to content that’s quite unique.

URLs Explorer - 2

Another common canonicalization mistake we find is canonical tags that point to non-compliant URLs. That means that the URL is canonicalizing to a page that has been redirected, deleted, or has been no-indexed. This type of signal is confusing to Google because you’re essentially saying “don’t index this page, index this redirected/broken/no-indexed page instead.”

URLs Explorer - 3

You want all canonical tags to point to compliant pages — pages that don’t have errors, haven’t been redirected, and aren’t marked as no-index.

10. How do I check that my canonical tags are accurate?

Going page-by-page through your website to check your canonical tags isn’t feasible. Enterprise websites in particular need a scalable solution.

Botify checks for common canonicalization mistakes and has reports that give you visibility into whether or not your canonical tags are following best practices. The platform shows you everything from content similarity between a page and its canonical to pages that canonical to a URL with errors.

To learn more about the technical capabilities of the Botify platform, read about our technical SEO use cases or book your own walkthrough of the platform today!