The executable is /usr/bin/epiphany-gecko. There is also a lib containing plugins: /usr/lib/epiphany-gecko/2.22/plugins/libdesktopfileplugin.so EDIT: before wasting too much time, I would look for an alternative to kompozer. Unfortunately, I'm of no help here - I just don't use WYSIWYG editors. (I then see what I get and never know how to get what I want...)