Wow, that sounds really annoying. A few questions:

(1) Are the duplicates appearing alongside the originals in the same folder? Or appearing somewhere else such as the Unsorted Bookmarks folder?

(2) Do you use Firefox Sync to synchronize your bookmarks with any other devices? If so, are they showing the same problem?

(3) Do you use any bookmark-related or backup-related extensions?

You can review what you have and check for updates (using the gear button) on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions.

To post a list of your extensions here, it's easier to get a list from the Troubleshooting Information page. Either:

• Help > Troubleshooting Information
• type or paste about:support into the address bar and press Enter

In the upper left is a button to "Copy text to clipboard". When you paste here, you'll notice a ton of other data which probably isn't needed, so you could delete the section called "Important Modified Preferences" and what follows before posting.

Are you using Firefox Sync?

• https://support.mozilla.org/kb/what-firefox-sync

What Firefox extensions are you using,

• please list them
• does this include xmarks ?
• you will be able to copy the listing from the Troubleshooting Information page
  Use Firefox Button -> Help -> Troubleshooting Information
  See Use the Troubleshooting Information page to help fix Firefox issues

N.B. A potentially related thread /questions/980749

My post above is currently marked as the solution. I will unmarked it as that may have been selected in error.

However it is possible the other thread at least provided a workaroud:

• use the addon https://addons.mozilla.org/firefox/addon/bookmark-deduplicator/
• (or possibly even that uninstalling xmarks helps )

vmimi24

Would you like to comment please, is using the above add-on a workaround that helps with this issue ?