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Canonicalization is a method used to help prevent duplicate content issues and manage the indexing of URLs in search engines. Using canonicals appropriately can be hugely helpful for SEO.

Implementing the canonical tag link attribute “rel=canonical” is a signal to search engines about the preferred page for indexing, and will be followed in most cases when it is correctly implemented to an equivalent page.

The collected SEO Office Hours notes below provide detailed information and best practices (straight from Google’s own search experts) for using canonicals on your website.

For more on canonical tags and related topics, check out Lumar’s additional resources:

Content on Canonicalised Paginated Pages Will Be Lost

Unique content and links on canonicalised paginated pages will be lost if Google accepts the canonical directive.

6 Oct 2017

Update Internal Links to Canonical URLs

Update internal links to canonical URLs to give Google a clean signal about which URL to index. If the canonical is accepted, any links to canonicalised URLs will be associated with the canonical URL.

6 Oct 2017

Low Proportion of Indexed Pages Points to Technical Issue

If a site has a low proportion of indexed pages, this usually points to a technical issue than a quality issue. Compare the site map index counts and index status report for differences. Try splitting up sitemap file , checking indexed pages using info: query, that rel canonicals match those in sitemap file, hreflang and internal linking. Also, uppercase, lowercase, trailing slashes all matter. Then check crawl stats to get idea of crawl rate and if it’s reasonable.

22 Sep 2017

Align Linking & Rel Canonical If Want Particular Page Indexed

Ensure internal links and rel canonical are pointing to preferred page to ensure you aren’t giving Google conflicting signals about which page should be indexed.

25 Aug 2017

Google Takes Rel Canonical To Be Mistake If Present With Noindex

If a canonical and noindex are both present on a page, Google’s algorithms judge the rel canonical to be a mistake and the noindex as being used as a way to force a canonical.

11 Aug 2017

Internal & Sitemap Links May Override Canonical Tags

Google uses a number of factors to determine which URLs to show. Canonicalised pages may still be chosen if you link to them internally and in Sitemaps.

7 Jul 2017

Add Self-Referential Canonical Tags

Add self-referential rel canonicals to pages as it gives Google a clear indication of what page is to be indexed. Even if there is just one page, there may be different variations such as parameters – a rel canonical will clean these up.

7 Jul 2017

Search Console HTML Improvements Are Created Before Canonicals Are Processed

HTML Improvements in Search Console are generated when pages are initially crawled, but before a canonical tag is processed so they can be ignored for canonicalised pages.

7 Jul 2017

Use Canonical Tags to Test a New Website Before Migration

When you want to test a new website in parallel with the old one, you can launch the new site on a sub-domain and canonicalise the new pages to old pages.

30 Jun 2017

Content in Iframes May be Indexed on the Embedding Page

Pages embedded within an iframe on another page may be indexed as content on the embedding page as it will be seen when the page is rendered. You can use X-Frame-Options to prevent browsers from embedding a page which Google will respect.

30 Jun 2017

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