Myth: subdomains and subfolders are treated identically by Google

Myth: subdomains and subfolders are treated identically by Google

Google's public line — "we're fine with either" — gets quoted to mean the choice is neutral for authority. The observed data is messier than the official line.

Google says it can associate a subdomain with the root domain. "Can" is doing heavy lifting. Multiple documented migrations (HubSpot's blog, and others moving blog.example.com to example.com/blog) reported traffic gains after consolidating to a subfolder. The mechanism: subfolders share the parent's authority signals more reliably; subdomains are sometimes evaluated as semi-separate sites.

— For an authority play where you want one domain's signals concentrated, subfolders are the safer default
— Reserve subdomains for genuinely distinct properties (app, support, store) you don't need ranking on core topics

Caveat: migration case studies are confounded — a move triggers re-crawl, redirects, and cleanup all at once. The folder change alone can't be cleanly isolated. The directional pattern is consistent enough to act on.
Confidence: medium