Press Ctrl + Show Windows. Show Windows is usually on the top row and looks like a rectangle beside two vertical lines. If your keyboard has a dedicated screenshot key, use it to open the Screen Capture toolbar and select the full-screen option.

Press Shift + Ctrl + Show Windows to open Screen Capture. Select the screenshot icon if the toolbar is in recording mode. Choose partial screen and drag around the area you need, or choose window and click the window. On an external keyboard without Show Windows, Google lists Ctrl + Shift + F5 as the toolbar shortcut.

Open Files → Downloads to find the saved image. If it isn’t there, open Screen Capture settings to check the selected folder. You can also open Screen Capture from the Quick Settings panel by selecting the time at the bottom right, which is useful when you’re using the Chromebook as a tablet.