Starting April 14, 2020, sites without a custom domain are being moved from site-name.netlify.com to site-name.netlify.app . Traffic to any site-name.netlify.com address will be forwarded to site-name.netlify.app using an HTTP 301 redirect. New websites will also have URLs ending with netlify.
https://news.ycombinator.com/item?id=22853586
origin - https://www.pipiscrew.com/2020/04/apps-hosted-on-netlify-com-to-redirect-to-netlify-app-starting-april-14-2020/ apps-hosted-on-netlify-com-to-redirect-to-netlify-app-starting-april-14-2020