You can then approve (checkmark) or revoke (uncheck) apps and try again. You can change any of these settings by clicking the lock at the bottom of the screen, and then authenticating with your administrator password (or Touch ID, or Apple Watch). If the box is empty, permission was denied. If there’s a checkmark in the box next to them, they’re approved. Any apps that have requested access will be listed here. You can give any app permission to access your webcam by heading to System Preferences > Security and Privacy > Camera. It’s easy (and often sensible) to deny access at first, but this can pose a problem when it comes to making video calls or recordings. When you open an app that wants to access the webcam for the first time, macOS will prompt you to allow it to do so. It’s easy to apply a cover and forget about it, especially if you don’t use your webcam frequently. If you’re not getting any errors, and all you see is a black screen, make sure there isn’t anything covering your webcam. Many people cover their webcam when it’s not in use to protect their privacy. It might sound obvious, but if your webcam isn’t working properly, the lens might just be blocked or covered with something. It’s always best to check the basics first.
