How to find duplicate files and remove them on Windows or Mac

Most duplicate files are not a mystery. You downloaded the same attachment twice, copied a folder as a backup and forgot about it, or imported the same photos again. The trick is to find the extras without deleting the only good copy.

This guide shows you how to find duplicate files by hand on Windows and on a Mac, and then how to ask Key to help with the looking.

Before you delete anything

A few habits make this job safe:

• Start small. Pick one folder, such as Downloads or Pictures, not the whole computer.
• Never touch system folders. Stay in folders that hold your own files: Documents, Desktop, Downloads, Pictures.
• Use the bin, not a shortcut. Send files to the Recycle Bin (Windows) or the Trash (Mac) and leave them there for a week before you empty it.
• Check, then delete. Two files with the same name are not always the same file, and two files with different names can be identical.

How to find duplicate files on Windows

File Explorer can show you everything you need to spot copies. You are looking for files with the same size and the same date.

1. Press Windows + E to open File Explorer, then open the folder you want to tidy.
2. Choose View › Details so you can see Size and Date modified in columns.
3. Click the Name column heading. Files with similar names now sit next to each other, so holiday.jpg and holiday (1).jpg are easy to spot.
4. Click the Size heading too. Two files with exactly the same size and the same date are very likely the same file.
5. To be sure, right-click each one and choose Properties, or just double-click both to open them and compare.

Remove the extras on Windows

1. Click the copy you want to get rid of. Keep the one with the clearest name or the one stored in the right folder.
2. Press Delete. The file goes to the Recycle Bin, not away for good.
3. Open the Recycle Bin on your Desktop to look over what you removed. If you made a mistake, right-click the file and choose Restore.
4. A week later, if nothing is missed, right-click the Recycle Bin and choose Empty Recycle Bin.

If you only want to see where the space is going, open Settings › System › Storage. It shows what is using your drive, which tells you which folders are worth checking first.

How to find duplicate files on a Mac

Finder works in a very similar way. It also has a saved search that gathers one kind of file in one place.

1. Open Finder and go to the folder you want to check.
2. Choose View › as List.
3. Click the Name column heading to put similar names side by side, then click Size to group files of the same size.
4. To compare two files, click one and press the Space bar for a Quick Look preview. Press it again to close.

If you want one view of every file of a certain type, such as all PDFs, make a smart folder:

1. In Finder, choose File › New Smart Folder.
2. Click the + button near the top right.
3. Pick Kind and choose the type, for example PDF or Image.
4. Sort the results by Name or Size and look for pairs.

Remove the extras on a Mac

1. Click the copy you do not need and press Command + Delete. It moves to the Trash.
2. Open the Trash from the Dock. To get a file back, right-click it and choose Put Back.
3. When you are sure, choose Finder › Empty Trash.

Duplicate photos in the Photos app

If your pictures live in the Photos app, it finds copies for you.

1. Open Photos and look for Duplicates in the sidebar under Utilities. If you do not see it, hover over Utilities and click the arrow beside it.
2. Select the items you want to deal with. Press Command + A to select all of them.
3. Click Merge and confirm in the box that appears.

Photos keeps one copy and moves the extras to Recently Deleted, where they stay for 30 days in case you change your mind.

Asking Key to help you look

Hunting through folders is the slow part. Key can do the looking for you. You tell it what you are after, in words or by typing, and it opens the real folders and finds files by what is inside them, not only by the name. That helps when the same document has been saved under two different names.

If more than one file matches, Key asks which one you meant, so you stay in charge of the choice. Anything it removes goes to the Recycle Bin or the Trash. Key has no permanent delete at all, so a wrong choice can always be undone.

KeyChat

Find my March electricity bill. I think I saved it twice.

searched Documents and Downloadsread the matching filesfound two bills from March

I found two files that look like your March electricity bill. Which one would you like to keep?

Checked: opened both files and read the dates and amounts inside.

While it works, a small panel shows what it is doing, and you can stop it at any point. When it finishes, it reads the result back before it tells you it is done, and if it could not check something, it says so.

For more help with finding things, see how to find a file by what is inside it. If your Downloads folder is where most of the copies live, how to clean up your Downloads folder without losing anything goes further.

A simple routine that keeps copies away

• Save a file once, in a folder you will remember, and move it rather than copying it.
• When a download ends in (1), check whether you already have the first one.
• Look through Downloads and Pictures every month or two. Short, regular clean-ups beat one huge one.
• Wait before emptying the bin. A week is plenty.

Done carefully, this takes a few minutes per folder and can give back a surprising amount of space.

Related guide: How to organize files into folders by type, date or name

Related guide: How to delete temporary files in Windows 11 and free up space

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