How to find and delete duplicate files on the Mac’s disk

Duplicate files are a waste of space. They use megabytes or even gigabytes of disk space and serve no purpose, so why not hunt them down and delete them? It will free up space for other things.

Duplicate file can occur for all sorts of reasons and sometimes we download a file, move it to another folder, and download it again a week later either because we forgot we had done it or we forgot where the original was.

Sometimes we make copies of files we intend to change, such as a document, but we never get around to it, or we start, but don’t finish.

We might make backups and then forget we have done it or where we put them. We might save email attachments for the same reasons.

There are many reason why duplicates arise, but how do you check whether there are any on the disk? One method is to use a free utility called dupeGuru (https://www.hardcoded.net/dupeguru/).

Scan the disk with dupeGuru

Run dupeGuru and if you want a general scan, select Standard for the Application Mode.

The Scan Type can be Filename, Folder or Contents. The most useful is Contents and this will find duplicate files that have different filenames.

Click the plus button in the bottom left corner and select the folder you want to scan, such as the Documents folder. Subfolders are included.

Check the results

Files (in blue) and their duplicates below are listed. Click the boxes to tick the items that are to be removed.

Tip: Click a column header to sort the files by that attribute. Click again to reverse the sort. For example, click Match % (twice) to show the file that are 100% identical at the top. Click the Size header to sort files into order with the biggest at the top, so you can select them and save the most disk space.

If you are not sure about files, you can right click them and choose Reveal Selected in Finder. A finder window opens and you can check the file.

The Finder Quick Look function is included and selecting a file and then clicking the eye button displays it. This is especially useful with images and you can view identical ones and confirm that they are the same.

Remove duplicate files

After selecting duplicate files by clicking the tick boxes, go to the gear icon and there are several options. You could send them all to the Trash or you can create a folder and use the Move Marked to option.

If you discover that you needed a file after all, it can be recovered from the Trash or the folder you moved it to.

Final thoughts

Be very, very careful what you delete. There are sometimes good reasons why there are duplicate files and a backup folder is by definition a duplicate. Deleting all the files in a backup would mean you no longer have a backup.

If a project you are working on uses a set of files that are similar to other projects, you might select and delete the duplicates and then have an incomplete set of files for a project.

Using the option to search for duplicate filenames is not recommended because we often use the same filename for things. For example, if you design a graphic logo, you might change it and save the updated logo with the same name elsewhere. The filenames could be the same, but the contents are different.

Use a content search to ignore filenames when searching for duplicates.