Previous macOS versions allowed you to control what apps can access your location, contacts, photos, calendar and reminders. macOS Mojave adds the ability to control what apps can access your camera and microphone.

So the 1st time Chrome, Slack or Zoom will try to access your camera or microphone you will get a prompt from macOS:

macOS Mojave asking you whether you want to allow Zoom to access your camera

The prompt will not show for some Apple apps like Safari, FaceTime, Photo Booth and even Safari Technology Preview as they're allowed by default. QuickTime on the other hand will trigger the macOS prompts for camera & mic access.

The answer to the prompt is persistent and the app will be listed in
System Preferences > Security & Privacy > Privacy > Camera .

List of apps that have asked for camera access in macOS Mojave

Apps with access to the camera will have a check mark in the above list. You can revoke access by unchecking the app you want to revoke access to. There's a separate list for apps which have requested microphone access.

macOS will only prompt you once for each app. It will not prompt you again about apps in the list. If you want to change the permission for these apps, you will have to do it from the list above.

You can however reset the entire camera and microphone access list by issuing the following commands in the Terminal: tccutil reset Camera and tccutil reset Microphone

These 2 commands will reset the camera and microphone access lists in macOS Mojave
Empty list of apps which have requested camera access in macOS Mojave. Apps like Safari & FaceTime still have access to the camera & microphone even if they do not show up in this list.

OS Level vs Browser Level Permissions

The (OS level) prompt & permission above is different from the (browser level) prompts and permissions you get in Chrome and Firefox for each domain.

For example when trying to record a video in Chrome with the Pipe video recorder on a fresh install of macOS Mojave you'll first be asked by the browser to allow the domain to access the camera and microphone:

Chrome asking us whether we want to allow this domain to access our camera and microphone

and then by macOS for permission to access the microphone (1st macOS prompt):

macOS asking us whether or not we want to allow Chrome to access our microphone

and camera (2nd macOS prompt):

macOS asking us whether or not we want to allow Chrome to access our camera

If you block the browser level permission you will not get the OS level prompts.