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John Mueller of Google shares when to use subdomains
2022 December 2
He said that it depends on what you’re trying to do. Is it content that’s meant to be tightly connected to the main site? Then put it on the main site. A subdomain is a good match if you want the content to stand independently.
Source: https://www.seroundtable.com/google-seo-subdomains-34449.html