In a Zoom meeting, the host and other participants can easily share their screen using Zoom’s Share Screen function, provided the host of the meeting has enabled the option for everyone. However, when you enter a Zoom meeting, the host and the participants can not view your computer or mobile screen. They can only see your video and hear your audio if you have enabled those in the settings.
For others to view the screen on Zoom, the person who wants to share the screen needs to give permissions by enabling the Share Screen option.
There is no other way the host or other participants can view your screen without permitting them by enabling the share screen option.

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What can the Zoom host and participants see during screen sharing?
In a Zoom meeting, you can share the screen in various ways. You can either share the entire screen or share a portion of your screen.

When you share the entire screen, the Zoom host and other participants can view everything you are doing on your computer. Therefore, it is advisable to be careful in opening personal files.
In case you choose to share a portion of the screen or browser tab, then only that portion will be visible to the host and the other participants in the meeting.
Also read: How to mute yourself on Zoom? How to turn off the video?
How to know if my screen is shared with the host and other participants?
When you start sharing your screen with the host and other participants in the meeting, a green colour border will appear on your PC screen. You can also see a message on the green band on the top saying, “You Are Screen Sharing”.

To disable screen share, click on the Stop Share button.
On iOS device
When you start screen share on your iOS device, you will see a “You Are Sharing Screen” message on the Zoom app and a red broadcast icon will appear on the status bar at the top.

On Android device
Similarly, when you start screen share on your Android device, you will see a broadcast icon on the top of the screen and a screen sharing menu at the bottom of the screen.
Also read: How to find Zoom recordings?
Can the Zoom host or participants control my screen during screen sharing?
The screen sharing functionality of Zoom application does not work as a desktop remote. Therefore, the host or the participants cannot fiddle with your files, apps or emails as the control only lies with the person sharing the screen.
However, when you open any such files or apps, then the host and the participants can definitely view what is on it but can not control it at any cost.
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Can the host or participants know what I’m doing in a Zoom meeting?
Earlier, Zoom application had an attention tracker feature to know if the attendee is paying attention or doing something else during the meeting. However, due to security and privacy concerns from the customer the same feature was removed on April 2, 2020.
If you are worried about what if your boss can see that you are using your phone and not paying proper attention during a Zoom meeting or webinar, then be rest assured that he cannot see you or track your attention unless you have kept your video on and in that case, he will be able to see you via the video feed.
Also read: How to share audio on Zoom?