Canonicalization is a method used to help prevent duplicate content issues and manage the indexing of URLs in search engines. Implementing the canonical tag link attribute “rel=canonical” is a signal to search engines about the preferred page for indexing, and will be abided to in most cases when it is correctly implemented to an equivalent page. Our Hangout Notes on canonicalization provide best practice advice and insights for how it is handled by search engines.

JavaScript Injected Tags Should Not be Duplicated in Static HTML

August 24, 2018 Source

Using JavaScript to modify canonical or robots meta tags can change the signal provided to Google when they come to process the rendered version of the page. If tags are injected using JavaScript, then John recommends not having them in the static HTML so that the signal provided to Google is clear.

Google Doesn’t Support Canonical Tags for Images

June 26, 2018 Source

Canonical tags don’t work for images, so you can’t fold together different sizes of an image to make sure only the best size is indexed, for example. Google is looking into how best to use srcset for image search, however.

Canonical Selection Doesn’t Affect Rankings For a Group of Pages

June 26, 2018 Source

Google will simply show one URL out of a group of pages that have been canonicalised. The ranking will be the same for that group of URLs no matter which one Google decides to show.

Different Signals Determine Google’s Canonical Selection

June 26, 2018 Source

John confirmed that rel canonical, redirects, internal linking, URL parameters and sitemaps are all signals Google uses to decide which page is the canonical from a group of pages that have been folded together.

Canonicalise Duplicate Pages Between Your Sites so They’re Not Seen as Doorway Pages

May 29, 2018 Source

Use the canonical tag if you are offering the same products on lots of different sites so Google doesn’t suspect that these are doorway pages.

Make Sure A Separate PWA is Canonicalised to Your Mobile Site

May 29, 2018 Source

Google won’t get confused between your main site and separate PWA as long as you have canonicalization in place.

Internal Linking Causes Google to Crawl Canonicalised Pages

May 29, 2018 Source

Check your internal linking if you see Google crawling canonicalised pages.

Hreflang Should be Included Between the Canonical Versions of Pages

May 18, 2018 Source

Including hreflang on paginated pages is fine but the most important thing is to include hreflang tags between the canonical versions of the page.

Parameter Handling Signals Are Stronger Than the Canonical Signal

May 15, 2018 Source

Google won’t blindly follow URL parameter handling set in GSC, but John says that this is a stronger signal than using canonicals.

Related Topics

Crawling Indexing Crawl Budget Crawl Errors Crawl Rate Disallow Sitemaps Last Modified Nofollow Noindex RSS Fetch and Render