When you take screenshots on a Mac computer, the default file format is PNG. PNG is a lossless file format; it stands for Portable Network Graphics. It’s great for showing high quality images, but can also create large file sizes of several megabytes. Why should you care?
Sending an image of several megabytes by email or text message poses no problem (unless your image is incredibly high resolution). However, if you’re posting an image on the web, a good goal is to have the image be around 200KB or less. This will allow the file to load quickly for visitors to the web page, even on slower connections.
JPEG stands for Joint Photographic Experts Group. It’s generally a loss format because it lets you apply compression to an image to reduce its size. Compression will decrease the resolution of the image as well as its size so you’ll want to check the quality of any JPEG images that you create. JPEG files may have the extension .jpg or .jpeg. The two extensions represent the same file type.
Changing File Formats in Preview
I use a lot of screenshots for blog posts and instructions for websites. Working on a Mac, I usually open the png file in Preview and then export it to JPEG, checking the size as I modify the quality:
If you’re making a lot of screenshots that you want to use on a website, you may want to set JPEG as the default format for screenshots.
How to Set JPEG as the Default Format for Screenshots on Mac
- Open Terminal (you can search for it in Spotlight)
- Copy and paste the following code into Terminal and press enter
defaults write com.apple.screencapture type jpg;killall SystemUIServerSet the Default Format for Screenshots on Mac back to PNG
- Open Terminal (you can search for it in Spotlight)
- Copy and paste the following code into Terminal and press enter
defaults write com.apple.screencapture type png;killall SystemUIServerOther Format Options
GIF
defaults write com.apple.screencapture type gif;killall SystemUIServerdefaults write com.apple.screencapture type pdf;killall SystemUIServer