Some frameworks will offer this as part of the development process with a development server. Mojolicious (Perl) for example ships with Morbo as a development

Some frameworks will offer this as part of the development process with a development server. Mojolicious (Perl) for example ships with Morbo as a development webserver, and Hypnotoad as a more enterprise ready one. One of the major differences is that morbo will take a path and auto-reload if any file in it updates, while hypnotoad offers zero downtime reloads, but you have to manually tell it to restart. Arguably a delineation like this is better, even if just a single flag separating the behavior in the server, since it allows production to not worry about some file copies/changes forcing lots of reloads that aren't needed, which isn't really a problem in most development environments.