--- a/.emacs-my	Thu Nov 26 23:35:06 2020 +0200
+++ b/.emacs-my	Sat Nov 28 15:09:11 2020 +0200
@@ -1465,7 +1465,12 @@
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 (message "browser")
 
+(defun my--browse-url-cygwin-firefox (url &optional _new-window)
+  (call-process "cygstart" nil nil nil "firefox" url))
+
 (cond
+ ((eq system-type 'cygwin)
+  (setq browse-url-browser-function 'my--browse-url-cygwin-firefox))
  ((equal window-system 'w32)
   (setq browse-url-browser-function 'browse-url-default-windows-browser))
  ((boundp 'debian-emacs-flavor)