Change the Screenshot Capture File Format
Mac OS X defaults all screenshots to PNG files. Changing the default file type of screenshot captures is really easy, all you need to do is launch the Terminal (located in /Applications/Utilities/) and execute a command string.
After you have launched Terminal, type the following command to change to JPG:
defaults write com.apple.screencapture type jpg
Most major image formats are supported including PNG, PDF, GIF, TIFF, and JPG. In this example we went with JPG since that is a common type of web graphic, but here are the others:
Change default file type to PDF:
defaults write com.apple.screencapture type pdf
Change default file format back to PNG (default):
defaults write com.apple.screencapture type png
Change file format to TIFF:
defaults write com.apple.screencapture type tiff
After you have executed the above command appropriate to the file type you want to set, you’ll need to kill the SystemUIServer for changes to take effect:
killall SystemUIServer
Now if you take a screen capture, it’ll appear as whatever file type you specified.
This advice appears in numerous places on the web. Unfortunately, it does not work. I think people just copy other people’s advice without checking whether it actually works or not.
alternatively, it means you are doing something wrong. if you don’t kill SystemUIServer the changes do not take effect.
i set mine to jpg a long time ago, png is too heavy and offers no advantages. it works fine.
Worked beautifully! Thank you so much! I was actually really upset that when I updated to Lion OSX,all of my screenshots were saved at png files, and the only way I could save them as jpg extensions was to literally duplicate the screenshot in preview (because Lion got rid of the “save as” option =/), and then save the copy as a jpg and delete the original. Such an unnecessary hassle. Glad I stumbled upon this!