I connected a client’s domain a week ago. Today he sent a screenshot of the old address, still serving the whole site.

A client's landing pages moved to their own subdomain last week. DNS done, certificate issued, canonical tag pointing at the new name, tracking rewired. Everyone started using the new address. This morning the client sent a screenshot: the hosting platform's default address, the one with the platform's name in it, still loading the full site. Not a redirect. The page itself, twice.

I checked. Both addresses answered with a 200. The platform normally bounces its default address to your custom domain on its own, and I had assumed that was happening. The site runs on a framework runtime that answers requests before the platform's automatic redirect gets a turn, so the bounce never fired. Every part of the setup was correct and one door I had never tested was standing open.

The reason this matters is not the duplicate itself. It is who still holds the old address. The client's browser history. Any link shared in a chat before the switch. The ad platform if a draft ad was saved with it. Search engines, if they got there first. A canonical tag tells crawlers which copy is the real one, but nobody arriving through an old link reads a canonical tag. To them the old address is simply where the site lives, and it works, so nothing prompts them to change.

Connecting a new name does not retire the old one. Those are two separate acts and the second one is easy to skip because the first one looks like completion. The fix took four lines: an explicit, forced redirect from the old address to the new, with the path and query string carried across so click IDs survive the hop. Verified with a request, not by looking.

The consistency version of this: a thing should have one address. Two addresses that both work is not redundancy, it is a claim that there are two things, and every system downstream will eventually believe it.

If you moved a site or a page to a new domain in the last year, open the old one in a private window. If it loads instead of bouncing, the move is not finished.

(Client unnamed. Redirect verified on both pages with parameters intact.)