Do the protocols work correctly for you from Sharepoint? For example:

• I click on a row that has an Excel document, use the menu under Open to Open in app, and Firefox understands (ms-excel://) and shows me the application chooser (I have the option to instruct Firefox to always use Excel).

• I click on a row that has a Word document, use the menu under Open to Open in app, and Firefox understands (ms-word://) and shows me the application chooser (I have the option to instruct Firefox to always use Word).

If the app doesn't get the full URL from Sharepoint, I wonder whether some setting or filter is interfering?

Note for anyone else reading: if ms-excel:// or ms-word:// links don't do anything at all or are "not understood", try my post from a few months ago: https://support.mozilla.org/questions/1265375#answer-1239993

Thank You for reply. Protocols are recognized correctly, Word is launched after opening docx in sharepoint, but if opened from Firefox Word shows error message "Sorry, we can’t open <DocumentLocation> because the server isn’t responding.". Opening ms-word:ofe|u|https://server/file.docx type link in IE or from shortcut on desktop works as expected. Links seem unaltered in firefox.

That's strange. Word gets the correct info, but can't open the remote file, only when coming from Firefox?

Does it matter whether Word was already running or was fired up by using the link?

Are there any custom privilege settings on the system such as modifying the default UAC level or using "Run as Administrator" with any of the relevant applications?

Problem is now resolved, unfortunatelly I'm unable to tell what was direct cause of it. What helped is reinstalling Firefox (it was newest version before anyway) and/or "refreshing user account" done by admins. I should have added that computer is in Active Directory with quite limited permissions. Thank you jscher2000 for suggestions.

Same issue here and lots of colleagues have this issue too. Downloading an update or a beta version doesn't help either. Until recently there were no issues with opening Word/Excel documents in the browser. Please fix this

What webdav server are you using? Files are openened in other browsers? What error message are you getting?

This is SharePoint online/Office 365. No issues in other browsers. Get this message: Firefox doesn't know how to open this address, because one of the following protocols (ms-word) isn't associated with any program or is not allowed in this context. The link usually open Word in the browser or triggers the desktop app, but shows the above message instead.

Hi mrs.von, let's continue in your new thread here: https://support.mozilla.org/questions/1273398