1. Select any folder or group you would like to check for duplicates (eg: All Documents).
2. Select the 'Tools' menu, and select the 'Check for Duplicates' option.
3. Sets of duplicates will then be shown. Think of a set as what the result of your merge will look like when you confirm it. You can double click a set to expand it and view each duplicate document individually.

Select a set and review the metadata in the right hand details pane. Any field which has a tick to the left of it has no conflicts, which means a merge will result in no data being lost. If there are no conflicts, you can click the 'Confirm Merge' button to merge the set.

If a field is un-checked, that means 2 or more duplicates in the set have conflicting data. Mendeley has tried to choose the best value to make merges as easy as possible, but it pays to run an eye over unchecked fields.

If any un-checked field looks incorrect, you can edit the field as you would normally, to input the correct data.

Alternatively, if you know that one of your duplicates had the correct metadata, but Mendeley has picked the wrong data for some reason, you can expand the set by double clicking (or clicking the expand arrow to the left), select the correct document, and tick the box next to the metadata you want to use. You can pick and choose data individually this way from any documents in the set, but be aware that when you check a box here, it will overwrite what was previously selected as the correct data for the merge.

Any merge you do in the de-duplication tool can be undone using the standard Edit > Undo. If you only realize quite a bit later that you've made a mistake, don't worry. When duplicates are merged, all old documents are put into the Trash, and a new document is created from the merge process, so assuming you haven't cleared your Trash, you can restore the original documents from there, and attempt the merge again.

1. Click 'Help' in the menu bar.
2. Select 'Create Backup'.
3. Specify where you wish to save your backup files.
4. The backup will be created and saved in the selected location.

Please note: this backup should be stored in your local drive. If you try to recover this backup in a future from Mendeley Desktop and the folder is linked to a cloud-based drive or folder, you may experience serious database recovery issues.

You can also create a backup manually, which is only advised in the case that you cannot access Mendeley Desktop.

1. Locate your database. Where your database files are stored varies from operating system to operating system. In order to locate yours, please follow the corresponding value:
   • Windows: %LOCALAPPDATA%\Mendeley Ltd.\Mendeley Desktop\
   • Mac OS X: /Users/<Your username>/Library/Application Support/Mendeley Desktop/
   • Linux:~/.local/share/data/Mendeley Ltd./Mendeley Desktop/
2. Copy this entire folder to somewhere safe. You can copy this to another computer, a USB stick, or another folder on your computer for safe-keeping.