webloc extension

If you just double click one, the default is Safari. Oddly, you can't change this file type with Get Info. But there's nothing to stop you from opening one in (for example) Firefox. You can drag and drop the .webloc file into an open Firefox window/tab, or right click on the .webloc file and choose Firefox.

If you right-click on that .webloc and choose Open With Firefox, it will open in that browser, or if you set your System Preferences > General > Default web browser to Firefox, double-clicking on that .webloc will do the same thing.

Sorry, I have macOS 12.2 and Big Sur 11.6.3, not Mojave in front of me. The solution is as I stated for these two operating systems because I tested it before posting. I don't have Catalina in the house.

I just powered up my Late-2013 iMac running Mojave 10.14.6 and everything I described in the first post also works correctly there. Even dragging and dropping the .webloc file onto a Firefox Dock icon opens it in Firefox.