I had an old website hosted under www. When it was decided to build a new website, to preserve the old content, the new site was built without a leading subdoma

I had an old website hosted under www. When it was decided to build a new website, to preserve the old content, the new site was built without a leading subdomain. The problem was that chrome cached www as the default for anyone who'd visited the old site, and had started hiding www from the address bar. I used Caddy to redirect all requests to the subdomain free site unless the request came with a referrer from that site, fixing the caching and allowing for free navigation between and within both the old and new site.