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

Open With saves me a whole lot of hassle. Some sites don't work properly in FF, so, using Open With I can quickly load the current page in Chrome or (perish the thought!) Edge. But still more useful and indeed important for me is that I can quickly load the current page in BlueGriffon, my web page editor, or in EditPad Pro. I use both these latter for working on my local version of my extensive five websites. Saves a huge amount of hassle!

One odd thing. Just lately, the toolbar icon for Open With has taken to repeatedly giving a warning message, that Open With couldn't make contact with the outside world (presumably meaning it couldn't make an Internet connection). But its permissions don't include being able to do so, so something is clearly screwy about this.

As another reviewer has remarked, it would be greatly helpful to have a facility for exporting / importing one's settings.

Update:
I found that this extension had ceased working, and presumably this was associated with the error message noted above. I followed a reasonable hunch and re-ran "[path]open_with_windows.py install", and that fixed it.

I would not be able to live without this extension! Thanks Geoff for putting in all the work into it. I have a handful of privacy friendly extensions installed like Umatrix and ublock origin and a couple of other othes that often times break websites that i'm visiting for the first time. Most of the time i don't want to bother customizing the rules for the website because i probably will not be visiting it again so i quickly open the page using a different firefox profile and continue with my workflow. Makes my life incredibly easy and am very glad to have donated the $10 to try to pay back for all the time that i have saved using this.

@Afzal
It still works here.
Firefox 116.0.2.

great.

please, create option to export/import all configuration.

Please, update the extension to the latest version of Firefox!

FF60.6 ESR x64 - I always used this extension to watch YT videos in Firefox (browser-independent, better volume control). It worked perfectly, 5 stars.
For the new Firefox now it needs some extra steps, but it's nothing too difficult.
The problem, however, is that here CMD.exe for security resons is only allowed to run with admin permissions, so this addon it's KO for me unless it will manage to use other methods :\

I get double entries for browsers. How to remove them?

Good Extention.
Some wish from me:
Is it possible to add "open with" to the context menu not only for the links on the page, but also for the bookmarks in the bookmarks menu too?

I am not some Mozilla Geek. I just wanted to get Thunderbird mail to open using Chrome instead of Firefox. I found this Add-On and tried to install it. However the instructions are terrible!!
When I try to set the Options all I get is a message "To complete installation:" with instructions that are WAY TOO LIMITED. I think I got Python installed by running the file when it downloaded.
But, I can't get the rest of the instructions to work. When I click "Test Installation" all I get is a cryptic, useless message.
So, if you are not familiar about how to install add-ons, you may want to save the frustration and skip this one!!

Still the best "open with" addon out there. Thanks a lot!