Does it work on WhatsApp on my phone?

Phones don't let apps add a camera, so live WhatsApp calls need a Windows 11 computer. On a phone you can make face-swapped video messages instead.

Will the other person know?

They see a normal video call. Only use your own face or one you have permission to use.

Yes. Set Chrome or Edge to use FaceLive Camera for web.whatsapp.com and reload.

Be someone else on your next WhatsApp call. Your new face follows every smile and blink, live, and the other person just sees a normal video call.

Install FaceLive Camera for Windows and open it.
Pick a face and press Transform.
In WhatsApp for Windows: Settings → Video & voice → Camera → FaceLive Camera. On WhatsApp Web, set the browser's camera to FaceLive Camera.
Start the video call.