Send each old page to its closest new page

How to do it

Build the map page by page. If several old pages merged into one, send each of them there. If nothing replaces an old page, let it answer 404 or 410 instead of redirecting. Search engines treat a redirect to an unrelated page, such as the home page, like a missing page.

How to check

A test reads the map. No entry points at / unless its source was a home page address, such as /index.html. Any target shared by more than five sources is listed for a person to confirm.