Closing your Mac notebook with a camera cover on it might damage your display. Designed to protect your privacy, Mac notebooks have a camera indicator light to let you know when the camera is on.
If you close your Mac notebook with a camera cover installed, you might damage your display because the clearance between the display and keyboard is designed to very tight tolerances. Covering the built-in camera might also interfere with the ambient light sensor and prevent features like automatic brightness and True Tone from working. As an alternative to a camera cover, use the camera indicator light to determine if your camera is active, and decide which apps can use your camera in System Preferences.
Watch for the green camera indicator light
Apple products are designed to protect your privacy and give you control over your information. The products and features include innovative privacy technologies and techniques designed to minimize how much of your data we — or anyone else — can access. And powerful security features help prevent anyone except you from being able to access your information.
The FaceTime HD camera built into your Mac computer is designed with your privacy in mind and uses a camera indicator light that glows green when the camera is active. So you will always know when the camera is on. The camera is engineered so that it can’t activate without the camera indicator light also turning on. This is how you can tell if your camera is on.
Control which apps can use the camera
As an added security measure, you can control which apps have access to the built-in camera. Before any app can use your camera in macOS Mojave or later, you must first give it permission. To see which apps have permission to use your camera and to revoke or grant app access, learn how to control access to the camera on your Mac in System Preferences.
If your work environment requires a camera cover at all times
If your work environment requires you to cover the camera on your Mac notebook, follow these guidelines to avoid damaging the display:
Make sure the camera cover is not thicker than an average piece of printer paper (0.1mm).
Avoid using a camera cover that leaves adhesive residue.
If you install a camera cover that is thicker than 0.1mm, remove the camera cover before closing your computer.
Reference by Apple Support