Do you use Firefox Sync to share passwords with another installation of Firefox? You may want to break the connection so that this deletion isn't duplicated across. (If it works that way... I don't sync logins.) You could check your logins.json file as follows: Open your current Firefox settings (AKA Firefox profile) folder using either * "3-bar" menu button > "?" button > Troubleshooting Information * (menu bar) Help > Troubleshooting Information * type or paste about:support in the address bar and press Enter/Return In the first table on the page, click the "Show in Finder" button. This should launch a new window listing various files and folders in Finder. Position Finder so you can still see the Troubleshooting Information page behind it, then drag and drop the '''logins.json''' file back onto that tab. Firefox should process for a moment and then show a structured tree of saved logins. Is there anything there? If logins.json got cleared out, you'll need to dig up a backup. Perhaps from Time Machine? I'm a Windows person, so the ways of Time Machine are a mystery to me, but in another thread, someone mentioned that it is somehow integrated into Finder so you may be able to see what older versions are available somehow from that very folder.