How to speed up your Mac by deleting duplicate files

If your Mac is starting to run slow the first thing to check is if you are running low on space. It’s generally advised that you should have 10% of your total space free on your Mac for the most optimum working. If you are down to your last few GB then it’s time to do some house work and grab yourself some space back. 

Over time, a Mac is likely to accumulate a large collection of duplicate files that take up this valuable space so that’s a good place to start. However, finding and deleting them can be time-consuming if you do it one by one, so in this article we show you quicker ways to cleanse your system of these delinquent doppelgängers.

Why do I have duplicate files?

In most cases these will be mistaken downloads (caused by clicking on a link twice), Mail and Messages attachments, a convoluted filing system, a bad habit of dragging things to your desktop, or a number of other possibilities. Unless you’re an unusually fastidious Mac user, duplicates are going to turn up one way or another.

How to find duplicates using the Finder

It is possible to locate duplicate files on your system by using the Smart Folders feature in the Finder.

1. Start by opening the Finder app.
2. Navigate to File > New Smart Folder in the menu.
3. Click on the ‘+’ button in the upper-right corner.

Now you can search for documents, photos, music, or several other files types. The key is how you sort the results. Ordering them by name should bring up any duplicates that are easy to spot. (If it’s not displayed in name order click on the drop down menu to switch to List view).

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Just remember to check the date to see if it is a true duplicate – you don’t want to delete the wrong version of an important document, for example. (If you can’t see the date right click and choose Date Added, you can even add Date Last Opened to make sure you pick the right one to delete.

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While this is doable, it’s far from ideal. One issue could be that you have given the same file different names and this method will not show that up.

It’s also a time consuming process and the time spent ploughing through the long list of files could be better spent by visiting the App Store and buying software that will find and safely delete the duplicates for you instead.

Best Apps for finding duplicate files on Mac

There are a number of duplicate file finders on the Mac App Store which will automatically search your system and recommend file doubles that can be removed.

Many are free, including Duplicate File Finder Remover and Duplicates Cleaner. You could also try the Find Duplicates feature of Parallels Toolbox, which offers a functioning free trial for seven days, and we like Gemini 2 from MacPaw which has a three day functioning trial.

Most apps offer similar features, in that you ask the app to scan your hard drive, then are presented with a list of duplicates, accompanied by the original file so you know which ones are safe to delete.

All of the apps listed above will certainly clear up some space on your Mac, and you can always start with the free ones then move up to a paid version later if you find the features useful.

Usually you’ll have to move to a paid version for advanced features such as deleting duplicate folders, hidden files and similar functions.

Gemini 2

One of our favourite duplicate removal apps, and one with a good level of positive feedback from customers, is Gemini 2: The Duplicate Finder, which is free to download and includes a free three day trial. It offers a Smart Cleanup feature for $19.99/£18.49 as an in-app purchase. While the name might be more in keeping with a dystopian sci-fi novel, the app is a powerful tool for your Mac.

Once you have granted permission to scan your folders Gemini 2 will go ahead and Scan for Duplicates. The scan of our 256GB drive (with about 150GB files) took about seven minutes. When the scan had finished it had turned up 12.63GB worth of duplicates.

Gemini 2 selected 45.6MB files automatically – these were duplicated photos. We were able to automatically delete these by clicking on Smart Cleanup.

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However, there were still GBs of files left that were ripe for removal. It is possible to sort through the duplicates choosing which version to keep. Click on Select More to go through all of the duplicates that Gemini has found. You can flick through these and choose the one you want to lose. It’s a bit of a drag that you have to do this manually, but it’s still easier, and more visual, than using the Finder. You can also choose to delete every instance of the file or photo if you really don’t need it.

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Since we were removing photos Gemini reminded us that we need to also remove the photos from Recently Deleted in Photos, alternatively we could wait 30 days for them to be removed automatically. You can review what was trashed and ‘Put back’ any files you have second thoughts about (but this step needs to be taken before you delete the contents of your Recently Deleted folder.)

Not only can Gemini find doubles of any files on your hard drive, but it also searches external drives and cloud storage services such as Google Drive and Dropbox. All this is accompanied by the ability to immediately replace any accidentally deleted files.

Read more about Gemini – and the firm’s other related apps, such as CleanMyMac X – on MacPaw’s website.

Duplicate File Finder

Duplicate File Finder can scan your Home folder, or you can choose a particular folder or drag files in. There are two versions of the software – a free and a Pro version. The latter adds a few extra features, such as the ability to merge folders, and restore removed duplicates. The Pro version costs $19.99/£20.99 for one Mac.

You’ll need to grant it permission to scan various folders and sections of your Mac. The software will then scan for duplicates with some fancy graphs representing the kind of files it has found.

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You can then click on the Cleanup Hints section to find some files to delete. At every step there is a detailed overlay showing you what to do. Just click on the x to remove it.

In each case you can review the duplicate before deleting. As with Gemini you can remove the duplicates or you can remove all versions of the file or photo. The Review and Remove option does let you see a visual of where the duplicated file was located, which might be useful.

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You can also choose Auto Select to pick the duplicates for you – you can even refine the selection. You get to review these before they are removed.

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Duplicate File Finder creates a Duplicates album in Photos, which you will need to delete within the Photo app. You will also have to remove these from Recently Deleted.

More advice…

For more decluttering tips, be sure to read our How to free up space on a Mac feature, and a separate article that explains how to empty the Trash on your Mac. We also have advice about how to remove duplicated music in iTunes (or the Music app).

We also have this guide to ways to speed up a slow Mac and How to delete Other storage on the Mac, How to delete System on the Mac, and an article that explains How to delete cache on a Mac.