When using dired in emacs, how can I open an url file in a web browser outside emacs?
You can add a key binding, such as
C-RET to open any files in system defined default external programs such as xdg-open on Linux and open on macOS. In this way, URL files are opened by default browsers. A detailed approach is available on ErgoEmacs: http://ergoemacs.org/emacs/emacs_dired_open_file_in_ext_apps.html