I kept checking back to the reviews in hopes of more info on the installation of "open with", and there it was. I put open_with_windows.py in my Windows\system32......opened a command prompt, which opened in the Windows\system32 folder, and ran the open_with_windows.py install, and that was it for me. I ran test installation in my Browser and Thunderbird, and it showed, "Found version 7.2.3 at C:\​Windows\​System32\​open_with_windows.py." I then edited the order of my four Browsers, with Firefox on top.
Thanks to all the reviews with the help, and thanks to the the Author of this addon!!

I love it. 👍👍👍
But there is one problem. In Firefox for Mac, if I select Safari that is not running, the URL will open in Firefox as well.
Open With 7.2.5/open_with_mac.py 7.2.4/Firefox for Mac 86.0/macOS 10.15.7

Amazing addon! I'm only missing the ability to select multiple tabs and open them on the chosen browser, instead of doing it manually for each tab! There's an open issue on the github repo asking for this already, just in case other users would like to show their interest on this feature.

Misleading description, This extension can also launch different application and media player . Superb

安装了python，还是不能打开

Sorry, this add-on has served me well in the past, but now it completely stopped working on Firefox (clicking the browser icons does nothing, and sometimes it the menu also displays the message "Open With can't connect to the outside world"). I of course would prefer to get support fixing this rather than leaving a low rating, but there doesn't seem to be any realistic way to request help.

Spiegazioni inutili, non sapete spiegare , istruzioni eseguite, non funziona nulla!!!!!

it works perfectly with firefox and chrome. But in Firefox Developer Edition , it can't detect browsers.