Address duplicate content issues across subdomains.

Duplicate content across subdomains is one of those problems that develops gradually and often without anyone noticing. The most common scenario: a staging subdomain (staging.yourdomain.com or yourdomain.webflow.io) is left publicly accessible and indexed after the live site launches. Now Google sees two versions of your site with identical content and splits its attention between them.

The result is diluted rankings. Links that should consolidate authority to your primary domain get split across both versions. Google may choose to rank the wrong version in search results. And if the staging domain has a different age or authority profile than your primary domain, the comparison works against you.

On Webflow specifically: the .webflow.io subdomain remains accessible after you connect a custom domain unless you explicitly manage indexing. Webflow sets the webflow.io subdomain to noindex by default, but verify this is actually the case. In Google Search Console, run a search for site:yoursitename.webflow.io to check whether any pages from the staging domain are appearing in Google's index. If they are, the noindex isn't working or wasn't applied.

For other subdomain setups (www vs root domain, m. for mobile, app. for an application): each subdomain is treated as a separate site by Google. If your mobile subdomain (m.yourdomain.com) serves the same content as your desktop site, you need canonical tags pointing from the mobile pages to the desktop canonical URLs, or better, use responsive design and eliminate the mobile subdomain entirely.

The fix for duplicate staging domains: confirm the staging domain is set to noindex and that your robots.txt blocks crawlers. Verify in GSC that no pages from the staging domain are indexed. For client handoffs, it's worth documenting this step explicitly — many agency projects have their staging domain indexed for months after launch because nobody checked.

Check for subdomain duplication in your monthly GSC review by running a quick site: search on any subdomains that exist on your account. This takes two minutes and catches a problem that can quietly suppress rankings for extended periods.