Do you mean folders on your computer? How did you save those before?

Perhaps you were using an add-on that modified the built-in features... an add-on that wasn't updated for Firefox 57...

You could check on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions. Then check above the list for a link to "Show legacy extensions." If you see that link, go ahead and click it, and see whether there are any disabled extensions related to downloading/saving. Anything leap out at you?

It wasn't an ADD-on. I saved them in Downloads in File Explorer. In my case, when I looked at the "3-bar" menu button > Options > General > Files and Applications, Firefox set 'Saved Files to Downloads' as the default option. This is where my files were saved and the Downloads folders are now all empty. They were all there prior to the updates.

Do you still have some download history in the Library? You can open that using either:

• Ctrl+j
• downloads arrow button > Show All Downloads

To the right of one of your older downloads, click the folder icon to open the containing folder and see where it is. If the folder icon is missing, that usually indicates that the download is no longer in its original location.

Firefox shouldn't make any changes to already saved files on the hard drive. Only when files are in the OS temp folder then the life span might be uncertain.

Firefox manages downloads in the Downloads folder in the Library (History -> Show All History)

• downloads are treated as history items: clearing history removes included download items and vice versa
• the Download button gets a blue highlight once all downloads are finished to make you aware that new downloads are available
• Pause and Resume can be found in the right-click context menu of an item

When files disappear from the hard drive then usually some cleanup software is responsible.

Solved

"cor-el said

Firefox shouldn't make any changes to already saved files on the hard drive. When files disappear from the hard drive then usually some cleanup software is responsible.