Taking a screenshot of a Mac screen is not difficult, but if you need to record a video, a TV program that runs on your Mac screen is a bit more complex. If you are looking for a solution to record Mac screen while viewing a TV program or any other video, I point out a feature that basically is not very complex, and is also integrated directly into QuickTime that allows you to record everything that appears on the Mac screen.
Forget about using third-party software or other cumbersome screen recording software and tools and read the step-by-step instructions below about how to record Mac screens using QuickTime.
How to record Mac screen
Step 1: Open the QuickTime software on your Mac.
Step 2: If you have the application on the Dock, click the right mouse button on the QuickTime app and click on New Screen Registration.
Step 3: Or, click on File> New Screen Recording (^ ⌘ N).
Step 4: Click on the red Screen Recording button.
Step 5: Click to record the Mac screen entirely, or drag with the mouse to record only a specific area that interests you.
Step 6: To end the recording, click on QuickTime in the Dock with the right mouse button and click on Stop Screen Recording.
Step 7: Click on File and Save to save the recording as a MOV file.
If you followed this guide step by step, you’ve checked how simple it was to record Mac screen when a video was displayed. If in addition to recording Mac screen you also want to record the iPhone screen, Apple has introduced a new feature in OS X Yosemite that allows you to record an iOS 8 device with a Lightning cable in much the same way.
I hope this guide has been useful to you and if some passage is not clear you can ask in the comments.