Mueller concluded that subdomains generally don't hurt site rankings. He argued that Google's algorithms are good at crawling subdomains and subdirectories equally well and making sense of what you are trying to do.

Is it bad to use subdomains?

We don't mean to imply that using a subdomain is all bad. ... Separating them by subdomains can be very effective because they are treated as separate websites but still connected to the main domain. If you plan to produce a blog in multiple languages, subdomains may be beneficial.

Does having a blog on a subdomain affect SEO?

Do subdomains hurt SEO? When talking about where to host your blog, yes, subdomains hurt SEO. Placing your blog on a subdomain creates more work for your business and undermines your SEO strategy. Instead of optimizing a single site, you'll have the task of optimizing two sites.