Asking this question I thought I knew what this was about. That question was asking how to prevent Firefox from making files listed in its downloads list be opened with wrong programs. I still want to know that but now I realize I ignore more things than just that.

I thought I knew that the programs involved in opening files listed in the Firefox downloads list were determined under Settings/General/Applications. That is wrong. As said here that is for download actions: a choice between saving, opening in Firefox, in another application or asking what to do in relation to a file not yet downloaded. It is not about opening in a certain program an already downloaded file.

I also thought I knew the setting is reflected in the setting files usr/share/applications/defaults.list and/or /usr/share/applications/mimeinfo.cache. But they don't show the same options. Which one is determinant — if there is one?

For example, I have this Firefox downloads list:

enter image description here

The jpg and pdf used to be opened (if double clicked) in Vivaldi. After removing that, the image is opened correctly in Gwenview, but the pdf is opened in Chrome.

Checking usr/share/applications/defaults.list, I see the line: application/pdf=org.gnome.Evince.desktop;vivaldi-stable.desktop;google-chrome.desktop. I don't know what Evince is doing there given I'm in KDE Plasma and Evince was never installed, while Okular is the obvious default pdf viewer. As of the three apps listed only Chrome is really installed, that seems to explain the problem. (/usr/share/applications/mimeinfo.cache contains the line application/pdf=calibre-ebook-viewer.desktop;calibre-gui.desktop;google-chrome.desktop;libreoffice7.1-draw.desktop;okularApplication_pdf.desktop;.)

But not entirely, given that double clicking the docx file in that list it is opened in Calibre viewer. usr/share/applications/defaults.list shows the line application/vnd.openxmlformats-officedocument.wordprocessingml.document=textmaker-free21.desktop;textmaker-free21.desktop;libreoffice-writer.desktop. Textmaker is not installed. But looking up /usr/share/applications/mimeinfo.cache I have application/vnd.openxmlformats-officedocument.wordprocessingml.document=calibre-ebook-edit.desktop;calibre-ebook-viewer.desktop;calibre-gui.desktop;libreoffice7.1-writer.desktop;, which seems to explain it.

What exactly is the file that determines which app is used to open a file when double clicking it in Firefox downloads list?

1 Answer 1


The file ~/.config/mimeapps.list contains the same settings as those in Dolphin for default apps:


enter image description here

To set the Firefox option discussed here, check that first. (It's not that this file has priority over the others; in fact I've seen many wrong settings there that where not affecting Firefox; but when Firefox is affected by such things, there is a chance they come from there.)

If that doesn't work, edit ~/.local/share/applications/mimeinfo.cache.

Only if the above doesn't work edit usr/share/applications/defaults.list, and even /usr/share/applications/mimeinfo.cache.

Some particular cases may require a different solution, like for example for Thunar: here.

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