Preferred domain setting. The preferred domain setting is an old Google Search Console feature that has been part of the toolset since it was named Google Webmaster Tools. It let you communicate to Google the preferred domain is the one that you would liked used to index your site’s pages, which is also referred to as the canonical domain.
What it looked like. Here is a screen shot of that feature in the old version of Google Search Console:
No longer needed. Google is removing this feature because Google believe this is no longer needed. Google said it is able to pick the preferred domain for you based on various signals Google is picking up.
Current setting won’t be respected. Google said with this feature going away, Google will not look at the current configuration and setting. Google said “that with the deprecation we will no longer use any existing Search Console preferred domain configuration.”
What do I do now? You can now communicate to Google your preferred domain through good site architecture. Google said you can use these four methods or read this help document to help Google determine your canonical domain.
(1) Use rel=”canonical” link tag on HTML pages
(2) Use rel=”canonical” HTTP header
(3) Use a sitemap
(4) Use 301 redirects for retired URLs
Why it matters. If you are currently depending on Google to select your preferred domain through this setting, you can no longer depend on that. You will need to ensure that your canonical URL listed in Google has not changed with this announcement. Google did not say if it will communicate in any way to webmasters, publishers or developers through Search Console if this resulted in your site switching its canonical URL in Google’s index. Instead, you need to audit your Google results to ensure no changes were made.