Yes it can : https://support.mozilla.org/en-US/kb/applications-panel-set-how-firefox-handles-files

From Applications. If Zip is not in there install a zip program, allow for context menus. Try : www.peazip.org/

When Firefox comes across an unknown content type, it typically will ask you how you want to open it, and suggest the program(s) it found in the Windows registry. So you shouldn't need to do anything special for "application/zip" or other content types registered on your system by corresponding applications.

Some sites do not send the "application/zip" Content-Type header with a ZIP file and in that case, Firefox may not have a logical suggestion for how to open the file.

This is for downloading files via Airdroid. I have 7zip installed,

Never heard Airdroid that I know of?

How is Airdroid (https://www.airdroid.com/) connecting with Firefox? I'm not clear on which platform's settings are the important ones.

Airdroid is a mobile app. I use it mostly to transfer files from my phone to my desktop.

But behavior is the same elsewhere......

You're on Windows 7? Try this:

In Windows Explorer, find a ZIP file, right-click it, expand Open With, and click "Choose default program..." to change from Windows Explorer to your preferred zip program.

Does that work?

Firefox should follow Windows' lead after that.

It defaults to that program, but wants to open, not save, and hence won't allow 'do this automatically'. The program also does not show up in Options > Applications.

Does using the zip application change anything on the Options page?

If not, it is theoretically possible to edit the handlers.json file which stores download actions but it's just as possible to corrupt the file as to resolve the issue so I certainly can't guarantee results.

If you want to try it:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then right-click handlers.json and Copy. Then press Ctrl+v to paste and Windows should create a backup for you (handlers - Copy.json).

Now you'll want to open handlers.json in a text editor, preferably something that won't try to insert any formatting. You could try using Notepad. It might be easiest to launch Notepad from the Start menu, then drag and drop handlers.json into the blank document area to open it.

On Notepad's Format menu, enable Word Wrap if you can't see the end of the text, which should be

}}}

for example:

,"itmss":{"action":4,"ask":true}}}

You want to insert a new item as the last one on the list, before the last two }} characters, like so:

,"itmss":{"action":4,"ask":true},"application/zip":{"action":0,"extensions":["zip"]}}}

Before saving, turn off Word Wrap to avoid adding any new line breaks into the file. Then File > Save the document and File > Exit.

Start Firefox back up again. Does ZIP now appear on the Options page with Save File selected?

Firefox updated or something and the feature is present, so I was able to select 'save'.