By default, when you take a screenshot on OS X, it is saved as a PNG. There’s nothing wrong with this, but perhaps you prefer or need to take screenshots in JPEG format. For individual screenshots, you could open the image in Preview and then export it to that format.
This works, but it’s woefully inconvenient. If you need your screenshot to be consistently saved as JPEGs, then it’s better to simply change how OS X takes screenshots.
To do this, all you need to do is fire up Terminal and do a little command line hacking. In case you don’t know or have forgotten, the Terminal can be found in Applications > Utilities.
Type in the following command to change the screenshot format:
defaults write com.apple.screencapture type jpg
Then kill the system server with the following command so the change will take effect:
OS X doesn’t show file format extensions by default, but if you want to ensure that your changes are accepted, go ahead and take a screenshot and check its file info (Command+I).
You’re not limited to JPEG, either. You can elect to go with other file formats as well including PNG, PDF, GIF, and TIFF. For example, if you want all your screenshot automatically saved as PDF files, you’d simply amend the first Terminal command with “PDF”:
defaults write com.apple.screencapture type pdf
If you want to go back to the original file format (PNG), then you simply need to follow this procedure and place “png” at the end of the command.
defaults write com.apple.screencapture type png
Don’t forget however, to run the KILL command (
killall SystemUIServer ) to restart the system server or your changes won’t immediately take effect.
While it’s unlikely you’re going to change screenshot file formats often or regularly, it will come in handy for those odd times when a job or project requires screenshots to be in a specific format other than PNG.
If you prefer to have a little more control over every screenshot you take on OS X, you can always use the Grab utility, which will also let you save screenshots in your preferred file format as you take them.