Screenshots on the Mac take up too much space and are saved in the wrong location on the drive. Change the file format of screenshots to space-saving JPG and the folder they are saved to.
A screenshot of the Mac desktop with no windows open can be more than 10 MB. The file size depends on the screen resolution and the higher it is, the bigger the file. iMacs have the biggest desktop sizes and consequently they have the biggest screenshot file sizes. The smallest screenshot size is from a 13 in MacBook, but even that can be several megabytes.
If you take a lot of screenshots and need to keep them, they can end up occupying a lot of storage space. Several gigabytes of disk space may be used by screenshots and it can be a problem if storage is limited.
The default file type for screenshots in macOS is PNG, which is a lossless format that preserves the image quality perfectly. However, it also produces large file sizes.
An empty desktop on my MacBook Air is 10 MB, but with app windows open they are usually around 3 to 5 MB. This is because PNG files use compression and it works best with large plain areas like app windows. Anything complicated like the desktop wallpaper or a photo in a photo editor is hard to compress and results in screenshot files that are much bigger.
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Convert existing screenshots to JPEG
If you have a lot of screenshots already on your Mac and need to recover the space they occupy, convert them from the current file format of PNG to JPG.
Open a Finder window and go to the folder containing screenshots. Click the first to select it and then Shift+click the last to select multiple files.
Ctrl+click any selected file and choose Quick Actions > Convert Image from the menu.
Select the format, such as JPEG, set the image size to Actual Size if you want to keep them the same size, and click the Convert to JPEG button.
I converted 10 screenshots in PNG format occupying about 35 Mb to JPEGs occupying 5 MB, which is a big saving. What’s more, it is very hard to tell the difference between the original PNGs and the JPEGs.
Convert or save with Preview
One way to use less storage space with screenshots and to save them in an alternate file format is to use Preview. Double click a screenshot file in Finder after it has been saved and then export it from Preview to any of the file formats it supports, like JPEG, TIFF, PDF, HEIC and others. However, this means extra work is required after taking screenshots.
A slightly better method is to save screenshots directly to Preview. Press Shift+Cmd+5 and the screenshot toolbar appears at the bottom of the screen. Select Preview in the list of locations.
Now when you press Shift+Cmd+3 to take a screenshot, Preview opens with the image. It can then be exported to any of the supported file formats using File > Export.
Unfortunately, it is not always convenient when taking a series of screenshots to have Preview constantly interrupt what you are doing so you can manually export the image to the format of your choice. It also adds extra work compared to the next method I will look it.
Set the screenshot file format
The best way to take screenshots is to directly save them in the format you need. The default is PNG, but JPG, JPEG, TIFF, PDF are possible alternatives.
Open Terminal in the Utilities folder or press Cmd+spacebar and search for Terminal.app. At the command prompt, enter:
defaults write com.apple.screencapture type XYZ
Replace XYZ with JPG, JPEG, TIFF, PDF or PNG as you prefer. Use upper or lowercase as you prefer.
This updates the screenshot settings file stored at ~/Library/Preferences/com.apple.screencapture.plist. If you go to this folder in Finder, select it and press the spacebar, you can see the settings.
Change where screenshots are saved
Screenshots are saved by default in the Documents folder. However, you may prefer to save them elsewhere if you need to keep them. It is not convenient to clutter up the Documents folder with hundreds of screenshots. Create a folder for them. It could be a folder inside of the Documents folder, a screenshots folder could be created in your Pictures folder, or anywhere that is convenient.
Press Shift+Cmd+5 to show the screenshot toolbar and click Options followed by Other Location. Select the folder you want to store screenshots and click Choose. Press Esc to close the screenshot tool.
Try your new screenshot format and chosen storage location. Press Shift+Cmd+3 and then open Finder and check that the screenshot is there and in the format you want.