Capturing the current view of your Mac or iPhone can be useful for communicating exactly what you are seeing on your screen to someone. This can be great for troubleshooting and guiding someone on a specific procedure, but can also be useful for quickly preserving an image or some text you are seeing. Most Apple devices that display content support a screenshot option, and this can be invoked in most conditions to capture what you are seeing.
Mac OS X
On any Mac, you can press Shift-Command-3 to take a basic full-screen screenshot, and can press Shift-Command-4 to put your cursor in selection screenshot mode. In selection mode, you can click and drag to specify a portion of your screen, or you can press the Space bar to enter window screenshot mode, where clicking an entire window will take a screenshot of it. The screenshot ability in OS X supports a number of hidden options, such as for saving screenshots directly to the clipboard. You can see all of these options here.
While OS X has different screenshot abilities, you can still take a basic iOS screenshot in one of two ways. The first is to press the Power and Home buttons simultaneously, where you will see the screen flash and a screenshot should then appear in your Photos app. The second approach is to use QuickTime player to view your iPhone’s screen on your Mac, through which you can take a screencast and then export an individual image, or just take a window screenshot of the player view. You can read how to set up QuickTime for iOS screen capture in order to do this.
Apple’s newest computing device is its Apple Watch, and along with the others you can take screenshots of it. Similar to iOS, once the screenshots are taken they will appear as new photos in the Photos app, and then be accessible on a paired iOS device or through iCloud. To take the screenshot, press and hold the side button, and then immediately press the Apple Watch crown. As with iOS devices, the screen will flash briefly to indicate the screenshot has been taken.
For all screenshots, if your device has a Retina display, then keep in mind that the resulting screenshots will be double-resolution images. For instance, on a classic Mac, each shot will be at the standard 72dpi resolution, but those taken on a Retina MacBook or iMac will be at 144dpi. If this double-sized screenshot is displayed on an older system, then it may be rather large and require resizing or cropping.