There are lots of reasons why you might want to take a screenshot on your computer or phone: to prove you finally completed that video game, to record a website layout for safe keeping, or even to make some desktop wallpaper from your favorite movie. Whatever the reason, here's how to go about it on all the major platforms, from Windows to macOS and Android to iOS.
On Windows, a simple tap on the PrtScn (print screen) button will copy a shot of the desktop to the clipboard, and you can then paste it into an image editor.
There are other keyboard shortcuts to know about which make use of the Windows key (if your keyboard has one): press Windows+PrtScn and the shot is automatically saved into a Screenshots folder in your account's Pictures folder. Meanwhile Alt+PrtScn will take a grab of only the currently active window and copy it to the clipboard.
You can get help from various utilities too. If you locate the Snipping Tool in Windows (search for it from the taskbar), you can capture part of the screen or tell the computer to capture an image after a delay of five to 10 seconds. Alternatively, you can use the Game DVR tool in the Xbox app that comes with Windows 10 to capture grabs from games.
If you need even more options and features, tools such as Dropbox and Snagit can automatically back up and annotate your screenshots. Dropbox uses the same PrtScn key as normal but you can also hit Ctrl+PrtScn to get a shareable link to the screenshot you've just created.
Mac keyboards don't have a PrtScn key—or indeed a Windows key—so the shortcuts are completely different. Ctrl+Shift+Cmd+3 copies the current screen contents to the clipboard, or you can drop the Ctrl part to save a PNG file to the desktop instead.
If you just want to capture part of the screen, use Ctrl+Shift+Cmd+4. You can drag the mouse to outline an area of the screen or press the spacebar to capture a particular window. As before, leave out the Ctrl button and the image will be saved to the desktop rather than copied to the clipboard.
As on Windows, there are numerous utilities around to help you in your screen grabbing endeavors. Dropbox can handle screenshots using the same keyboard combinations, Grab is a handy app you'll find in macOS itself, and Lightshot Screenshot and SnapNDrag give you a few more options in terms of annotations and customizations.
The only app you can't capture from is iTunes. If there's a copyrighted movie or TV show playing on screen, macOS blocks all attempts to take grabs of these files, presumably for privacy reasons. So if you need freeze frames of films or shows, then you'll have to find another approach.
Android phones and tablets
On the majority of Android devices, you can press and hold the Volume Down button and the Power button together to take a screenshot. The screen should flash and you'll see a notification that a grab has been captured (tap this notification if you want to view or share the image). If you need to find the screenshot afterwards, it'll be in your device's Photos app.
That said, Android devices come with all kinds of manufacturer-made software skins running on them, so the shortcut might be slightly different depending on the make and model of your phone. On Samsung phones, you have to press Home+Power instead to take a grab; on Sony devices, you can just press Power to see a menu including a screenshot option (though Volume Down+Power still works).
The majority of HTC phones, meanwhile, support both Volume Down+Power and Home+Power for screenshotting purposes, so take your pick. If nothing seems to be working on your particular device, try a quick web search that specifies the make and model of your phone or tablet.
If Google Now is available on your Android device, you can also press and hold on the Home button then tap the Share icon to take a screenshot. On newer phones with the Google Assistant, swipe up from the bottom of the screen, rather than pressing the Home button, to find the screenshot option.
iPhones and iPads
Capturing the screen on iOS devices is just as easy as it is on Android devices: the combination you need is Sleep/Wake+Home. The screen flashes and the picture is saved to a dedicated Screenshots album on your iPhone or iPad. Then you can review or share it by opening up Photos.
While Android runs on phones and tablets made by multiple manufacturers, Apple makes all of its iOS devices, so these gadgets don't require multiple shortcuts. Sleep/Wake+Home is guaranteed to work across all iPhones and iPads running recent versions of iOS. As with macOS though, you'll be blocked from snapping grabs of iTunes movies and TV shows.
It's also possible to get your phone or tablet's display up on a computer and capture it from there. On macOS, connect your device via USB, then run QuickTime, and choose File and New Movie Recording. If you select iPhone (or iPad) from the drop-down menu by the red record button, the device's display will show up. To capture the window, use the Ctrl+Shift+Cmd+4, spacebar, and click combination we mentioned earlier.
On Windows, you can use an AirPlay client like LonelyScreen or Mirroring360, then broadcast the screen to your laptop or desktop using the AirPlay feature built into iOS: Swipe up from the bottom of the screen to open the Control Center and tap on AirPlay Mirroring to get connected.