https://developers.cloudflare.com/pages/configuration/serving-pages/#route-matching
If an HTML file is found with a matching path to the current route requested, Pages will serve it. Pages will also redirect HTML pages to their extension-less counterparts: for instance, /contact.html will be redirected to /contact, and /about/index.html will be redirected to /about/.
https://developers.cloudflare.com/pages/configuration/serving-pages/#route-matching