On Windows Vista and newer (Windows 7, 8 and 10), you can use the Snipping Tool built in to the operating system. In addition to capturing whole-screen images and individual app windows, this tool lets you draw a rectangular or free-form shape around the area of the screen you'd like to save. The image is copied to the Snipping Tool window for you to work on. You can find the tool by searching for "snipping tool" in the Windows search box, although the method for that differs depending on the edition of Windows you're using.
To use: In the Snipping Tool, select Mode (or the arrow next to the New button for older versions of Windows). Next select the type of snip you want. Mostly likely, you'll take Rectangular Snip. The screen will change slightly to gray and you can draw around the area you want to cut and save. Save it using the methods described earlier.
The Snipping Tool allows you to share and make notes on the screenshot you've taken, but Windows 10 has another tool, called Snip & Sketch, which adds additional annotating tools. You can search for it the same way you would with the Snipping Tool.
Originally Published: Apr 13, 2020