Anyone with a Mac computer can take screenshots without the need of any additional software. Using the Screen Capture keyboard commands, the Grap app and even Preview, Apple users can take screenshots of the entire screen, a part of the screen or specific windows. Note that some apps, like the DVD Player or some video games, may not support screenshots using any of these utilities.
Using Screen Capture Keyboard Commands
There are two ways to take a screenshot of a Mac computer using keyboard commands. Screenshots are saved as PNG images on the desktop, with the name "Screenshot," followed by the date and time.
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Press "Shift-Command-3" to take a picture of the entire screen.
To take a screenshot of a part of the screen, press "Shift-Command-4." This turns the cursor into a crosshair. Move the crosshair to one corner of the area you want to capture, like an image, menu or an app window. Hold the left mouse button and drag the crosshair to select an area. When you release the mouse button, the highlighted area is captured. Pressing the "Escape" key before releasing the mouse button cancels the process.
Changing Screen Capture File Format
By default, screenshots are saved in PNG format on OS X Yosemite. If you want to change this to another image format, you can do so in the Terminal app. The other supported image formats are JPG, TIFF and PDF. Launch Terminal, which is located in the Applications' Utilities folder. Type the following command in the Terminal window, using "jpg," "pdf," "tiff" or "png" as the last word in the command:
defaults write com.apple.screencapture type jpg
Replace "jpg" with the image format of your choice.
Using Grab to Take TIFFs
Launch the Grab app, located in the Applications Utilities folder. Once it's open, you can access the Grab app at any time from the Dock. When you're ready to take a screenshot, click Grab's "Capture" menu. The options there allow you to take a shot of the entire screen or select a specific area just as you would when using the screenshot keyboard commands. Additionally, you can take a picture of a specific window, which saves you trying to get the crosshairs directly over the window's edges. The fourth option is the Timed Screen screenshot, which gives 10 seconds before taking the picture.
When you capture a screenshot using Grab, it doesn't save the image automatically. Instead, it opens the image in a new window, which you can then save yourself as a TIFF file. Grab doesn't support other image formats.
Using Preview to Capture Screenshots
Apple's Preview app has the same screen capture options as the Grab app, with one small exception. When you take a screenshot of the entire screen, it always gives you a 10-second countdown. One advantage of using Preview over Grab is that you can use Preview's editing features before saving the image. The second advantage is that Preview doesn't limit you to TIFF images: you can save screenshots as PNG, JPG and PDF files, too. To take screenshots using Preview, click Preview's "File" menu, select "Take Screenshot" and then choose one of the three screenshot options.