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.

Useful extension but unfortunately it requires few extra steps maybe not easy to understand by basic users.

Donation made. Thank you 👍

If you are on macOS Catalina, install this extension and follow the instructions, but put the file "open_with_mac.py" in your "Public" folder. Only then it will work.

For people who cannot use it on macOS Catalina. I found a solution here, https://stackoverflow.com/questions/59543692/failed-to-connect-native-host-has-exited . In other words, download the helper program open_with_mac.py to $HOME/Public .
For debugging, I find it easier to debug with Chrome browser. There is a Chrome version of this extension https://darktrojan.github.io/openwith/

I was going to give 1 star. Till I realized I was in older python folder on main C Directory was wrong, I removed older versions and Launcher of Python from control panel (Programs and Features). and reloaded Python version 3.8.1 and noticed where it was loading it (Windows) >
C:\Users\xxx\AppData\Local\Programs\Python
I dumped the "open_with_windows.py" File downloaded from (On the Option Page when you click the toolbar button) I placed that file after downloading it in the Python folder and then Ran the "open_with_windows.py install" in Command Prompt Admin THEN Tested it via > Options on the Open With toolbar button got a green check and then it worked when I tried it on a web site page.

Finally, the installation is successful,Set the default open mode to Python,and use "open_with_windows.py install"
in the folder where the file is located. If you open any other windows when use "open_with_windows.py install" ,you should set the default open mode of .py file. Chinglish

Excellent.

Installed the add-on & helper on my Linux system, and found it very easy to manually add a lightweight browser (Qupzilla) to the list.

Not easy to install. tried doing this on my FF Portable. Installed the Python program and ran the command "open_with_windows.py install" Nothing happens and the open_with_windows.py file is opend in my text editor. When I click the Test Installation button get a cryptic message"Something went wrong. There might be more information in the Browser Console."

Extremely poor documentation. Don't know whether this works with FF Portable.

Thanks for the Plugin! Good but complicated. Have written a small tutorial in english and german. Maybe it helps someone.

DE: Gut aber kompliziert zu installieren. Wer Hilfe braucht kann es mit der kleinen Anleitung versuchen.

https://plugins.onkel-franky.de/tests/other-stuff/tutorial-firefox-plugin-open-with