The overlay is excluded from screen capture at the window-compositor level, which is what makes it invisible to Zoom, Google Meet and Microsoft Teams. That exclusion works on a per-window basis — and it stops working the moment the conferencing app captures something other than a window.
The usual cause
Zoom has a hardware-accelerated capture path that grabs the framebuffer rather than compositing individual windows. When that path is active, per-window exclusion has nothing to act on and everything on the display is shared, overlay included.
- In Zoom, open Settings → Share Screen and click Advanced.
- Turn off hardware acceleration for screen sharing. Depending on your Zoom version this is one checkbox or a set of three (for screen sharing, for video receiving, for video sending) — only the screen sharing one matters here.
- Fully quit Zoom and reopen it. The setting is read at startup.
Share a window, not a screen
The more robust habit, and the one worth building regardless of settings: share a specific window rather than the whole display. Window sharing sends only that window's contents, so nothing else on your screen can leak — not the overlay, not a notification, not the second monitor.
What stealth does not cover
- A webcam pointed at you, or a proctor watching your eyes.
- A separate recording device — a phone camera aimed at the monitor.
- Remote-desktop software that streams the framebuffer by design, rather than compositing windows.
- A locked-down proctoring browser running on a machine you do not control.
