Click Share in the control bar, choose a screen, window or tab, and confirm. Click Stop share to end. If the host has turned sharing off you'll see "The host has disabled screen sharing".
Mac: Screen Recording permission If macOS blocks sharing you'll see "macOS is blocking screen sharing for …". Open System Settings → Privacy & Security → Screen & System Audio Recording, turn on your browser (or KEZAYO, for the desktop app), then quit and reopen it and share again.
Desktop app The app opens its own picker: choose Entire screen or Window, pick a thumbnail and click Share.
Android app Tap Share and choose Entire screen or A file. For Entire screen, accept Android's screen-capture prompt (Android's own wording says "recording or casting" — it is the same thing as sharing, and everything on your screen is visible to the meeting, including notifications). Tap Stop share to end.
Share a file instead of your screen To show just a PDF or an image, choose Share a file (More menu on the web and desktop app, or Share → A file on Android), then pick the file (up to 25 MB). Everyone sees the pages in the meeting; as the presenter you turn the pages and everyone follows. The rest of your screen stays private. Only one file or screen is shared at a time, and the file stops being shared when you stop it or leave.
iPhone and iPad Apple does not let browsers (Safari or Chrome) share the screen on iPhone or iPad, and there is no iPhone app yet. Present with the Board instead, or share from a Mac, PC or Android phone.
Other browsers: if your browser can't share, use the KEZAYO app, or Chrome / Edge on a laptop or desktop.