In the Google SEO Office Hours June episode, a user asked how to avoid getting the syndicated versions of their content from appearing in Google Discover. This is because the syndicated versions of their content still show up despite using canonical links.
John Mueller answered that the link rel=canonical
is a signal which helps with canonicalization, as a hint. If you are syndicating your content and you do not want the syndicated versions to appear in search, he recommends making sure that the syndicated versions also include a noindex robots meta tag. This tag blocks the page from appearing in Search while still allowing users to access the page normally.
Mueller also mentioned that they have recently expanded their guidance for syndicated content to help cover this.
In the documentation, it mentions that articles in Google News are selected by their automated systems. If there are many versions of the same article, it can be difficult for their systems to identify the original article.
The canonical link element is not recommended for those who wish to avoid duplication by syndication partners, because the pages are often very different. The most effective solution is for partners to block indexing of their content.
If you syndicate your articles to other news sites or other sites within your own network, you can add this robots meta tag to your articles:
<meta name=”Googlebot-News” content=”noindex”>
This tag stops Google News from indexing the syndicated versions of your content.
To restrict syndicated content from both Google News and Google Search, other sites can add this robots meta tag to your articles:
<meta name=”Googlebot” content=”noindex”>
This tag stops Google’s main user-agent, Googlebot, from indexing your content.
Read more on this in this Google documentation.