I don't know how browsing hidden folders works in a Time Machine backup. In Mac OS X v10.7 and later, the ~/Library folder in the Home directory is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X
• ~/Library/Application Support/Firefox/Profiles/<profile>/

I see that my above posted reply didn't help.

Isn't there anything in the backup from your home directory (~/Library/Application Support/)?

If you did a fresh install of Firefox, it would have created a new profile folder with a partially randomized name. You can open the current profile folder from Firefox's Troubleshooting Information page. See: Profiles - Where Firefox stores your bookmarks, passwords and other user data.

If you ask Finder to look in a Time Machine backup for content from that folder, there won't be any because it's nearly guaranteed to be a new name. Could you ask Finder to check for backed up files/folders one level up, in the "Profiles" folder?

(This suggestion is based on how other users have mentioned using Time Machine; I generally use Windows.)

Files within the user Library (including ~Application Support/Firefox/Profiles, etc.) are hidden in Time Machine and as far as I know cannot be directly accessed. I tried using Search using the term "bookmarks" in attempting to possibly locate the the files. This turned up "bookmarks.json". I clicked "Restore", and got a prompt saying file already exists. I selected "replace" and action commenced. But this did nothing towards restoring the bookmarks.

Hi Keyless, where did that file restore to?

bookmarks.json sounds like a backup you may have created manually at some point. Firefox won't read a backup file automatically, you would need to use the Restore menu inside the Library window as described in this article (it would be Choose File and then point Firefox to that file):

Restore bookmarks from backup or move them to another computer

Firefox's self-generated backups have longer names like:

bookmarks-2018-05-10_6118_gibberish==.jsonlz4

Doing a search for “bookmarks” within Time Machine should have revealed all files with that keyword as part of the file name, including ones similar to what you have suggested. No such files turned up, only the generic one I mentioned. I also tried the “restore” instructions found on the Firefox website which was also repeated by helpful people in this thread. This also produced nothing. I’m pretty sure that files hidden in the Users/ Library folders cannot be accessed by Time Machine in the normal way. This is undoubtedly Apple’s idea of security. I would like to suggest to Mozilla to add a feature in Firefox to automatically backup bookmarks (and other important data) somewhere in the User area that is not in the Library.

jscher2000 said

Hi Keyless, where did that file restore to? bookmarks.json sounds like a backup you may have created manually at some point. Firefox won't read a backup file automatically, you would need to use the Restore menu inside the Library window as described in this article (it would be Choose File and then point Firefox to that file): Restore bookmarks from backup or move them to another computer Firefox's self-generated backups have longer names like: bookmarks-2018-05-10_6118_gibberish==.jsonlz4

What was in the file you found? You can drag/drop it onto this page to generate an HTML export you could view in a Firefox tab.

https://www.jeffersonscher.com/res/bookbackreader.html

For advice on accessing hidden sections of the Time Machine backup, you could try Apple forums or the many pages I see in web search results.