What the other side sees depends almost entirely on one choice you make in the first five seconds of the call: whether you shared a single window, a whole display, or a browser tab. Share a window and they see that window and generally nothing else, including nothing when you switch apps. Share a display and they see everything on it, now and for as long as the share runs: every window you open, every notification banner, the menu bar, Mission Control, the file you drag to the desktop. Share a tab and they see the page inside it and not the rest of your browser.
Everything else in this piece follows from that choice. Below is what each mode actually exposes, the leaks that catch people out regardless of mode, and a short checklist you can run in the minute before a call.
The three things you can share
One window
The narrowest option and the one most people underuse. You pick a window, and the share follows that window as you move and resize it.
What you gain is a hard boundary that does not depend on your own vigilance. What you give up is movement. If you switch to another app, the people watching do not follow you there. Depending on the conferencing app, they see the window you chose unchanged, a paused frame, or a placeholder. That is either the whole point or a genuine problem, depending on whether your call is a walk through one document or a tour of five apps.
Two details are worth testing rather than assuming. The first is what happens when another window overlaps the shared one, since a window capture and a region of the display are not the same thing. The second is what happens to a dialog or a file picker that the app opens: it may be a separate window, and a separate window is not the window you shared.
A whole display
The most common choice, and the one that carries the most risk, because the share is a place rather than a thing. Anything that appears on that display during the call is in the share, and you are the only filter.
This is the right mode when your call genuinely moves between apps, when you are teaching somebody the shape of a workflow rather than the contents of a document, or when you need to drag something from one app to another. It is also the mode where every other section in this article applies to you.
A browser tab
Offered by browsers and conferencing tools that run in the browser. The share carries the rendered page in that tab and not your other tabs, your address bar, your bookmarks bar, your extensions, or anything outside the browser.
It is an excellent fit for a demo of a web app and a poor fit for anything else, since the moment your work leaves the tab, the share stops being useful. Watch for the edges: a page that opens a new tab or a new window, a native file dialog, and a video played in a separate player are all outside the tab you picked.
| Mode | The far side sees | Notifications appear | Best for |
|---|---|---|---|
| One window | That window only, following it as it moves | Only if the banner is part of that window | A document, a deck, a single app demo |
| Whole display | Everything on that display, continuously | Yes, unless you have stopped them | Multi-app work, teaching a workflow |
| Browser tab | The rendered page in that tab | Only if the page itself shows them | Web app demos, anything browser-native |
The table is not an argument for one mode. It is an argument for choosing on purpose, because the default in most conferencing apps is the widest option.
Notifications, the leak that catches everyone
A banner from a messaging app is the classic screen-share accident. It arrives without warning, it sits above whatever you are presenting, and it can carry the first line of a message you had no intention of reading out loud. Handle it in layers, because each layer fails in a different way.
Focus
Turn on a Focus before the call rather than during it. Do Not Disturb is the blunt version and is usually the correct one for a call that matters. A Focus can also be set to turn on automatically, for example when a particular app is frontmost or on a schedule that matches your standing meetings, which removes the step you are most likely to forget.
Remember that Focus is about delivery, not about display. Something already on screen when the call starts is still on screen.
The system switch for sharing
In System Settings, under Notifications, there are switches governing whether notifications appear while the display is asleep, while the screen is locked, and while the display is being mirrored or shared. Find that last one and confirm what yours is set to. It is the single most useful setting in this article, and most people have never looked at it.
Do not assume it covers every case. It speaks to mirroring and display sharing, and the way your particular conferencing app asks macOS for the screen may or may not fall inside that definition. Test it: with a share running, send yourself a message from your phone and watch what happens on the far side.
Previews
Independently of everything above, you can set notification previews to appear only when your Mac is unlocked, or never, either globally or per app. This is the layer that saves you when the other two fail, because a banner that says only the name of an app is a very different disclosure from one that quotes the message.
The menu bar and what lives in it
When you share a whole display, the menu bar is in the shot. It is worth actually looking at yours as a stranger would.
- The clock and the date, which tell people your time zone and sometimes that your calendar is full of something.
- Status items from the apps you run, which can spell out which tools your company uses.
- Badged or expanded items, which can carry counts, connection states, or the name of a currently playing track.
- The application menu at the left, which carries the name of whatever app is frontmost and so quietly announces each app as you switch to it.
None of this is catastrophic on its own. It is worth knowing about because it is the part of the screen people forget is there, and because it is the one part that no per-window privacy setting can remove. A status item is drawn by the system into the menu bar, and the menu bar belongs to macOS.
If a particular item concerns you, the reliable fix is to remove it from the menu bar before the call, or to quit the app that puts it there.
Mission Control, Spaces, and switching apps
While a display share is running, the display is the subject. That includes the system interfaces that appear on it.
Opening Mission Control, invoking App Exposé, or spreading out every window with a trackpad gesture shows the far side thumbnails of what you have open, which is a faster inventory of your work than anything you would deliberately present. The same goes for the application switcher, which lists every running app in a row.
Spaces deserve particular attention. Moving to another Space during a display share generally takes the audience with you, because you have not changed which display is being shared, only what is on it. A full-screen app lives in its own Space, so entering and leaving full screen is a Space change too. If you keep a private Space with your own work in it, do not treat it as private during a share.
The honest summary for this mode is simple: you are not sharing a document, you are sharing a place, and everything you do in that place is visible until you stop.
A second display
A second display is the most common physical answer to this problem, and it works, with two conditions.
The first is that you share only the display you meant to share. Conferencing apps generally present each display as a separate choice, often as a thumbnail, and the thumbnails can be small and similar. Look before you click, and confirm afterwards with the far side.
The second is mirroring. The moment displays are mirrored, the second display stops being a separate place and becomes a copy of the first. Mirroring gets turned on for a projector in a meeting room and left on, and that is exactly the setup where nobody thinks to check.
One more thing to watch: window placement is remembered, and a window that normally opens on your second display may open on your only display when the second one is not attached. If you travel with a laptop and work at a desk with a monitor, the machine you use on the road is not configured the way your desk is.
Recordings and live shares are not the same risk
A live share is witnessed by people who are present. A recording is a file, and files travel.
The same capture path produces both, so anything visible in one is generally visible in the other. The difference is what happens afterwards. A banner that flashed for two seconds during a live call was seen by four people who were probably looking elsewhere. The same banner in a recording is on the timeline forever, can be paused, and will be watched by people who were never on the call, sometimes months later, sometimes by people you did not choose.
Treat recorded sessions as the stricter case. Prepare for them the way you would prepare for a published video, because that is often what they become.
The pre-call checklist
Run this in the minute before you present. It is short on purpose.
- Decide the mode. Share one window if one window will do the job, and only take a whole display when the call genuinely moves between apps.
- Turn on a Focus, and confirm the Notifications setting that governs sharing a display.
- Close or move anything private that is already on screen. Focus does not remove what is already there.
- Glance at your menu bar and quit anything you would rather not explain.
- Clear the desktop behind your windows if there is any chance of a window being moved, since file names are legible at share resolution.
- Check your browser: which tabs are open, what the address bar autocompletes to, and whether you are logged in as yourself or as a test account.
- Share, then look at the far side once, from a phone or a second machine, before you begin.
- When the call ends, stop the share explicitly and confirm it has stopped.
Steps two and seven are the ones that pay for themselves. Everything else on the list is easier than either of them, and less effective.
If you need to read something private during the call
All of the above is about what you keep out. There is a separate question: what happens when you need something on your own screen that the call must not include, for example a talk track, a name, or the number you are willing to go down to.
macOS has a direct answer for that case. A window can carry a property that keeps it out of every capture the system produces, so it stays on your display and never reaches the stream. How a Mac window stays off a screen share explains how the mechanism works and how to verify it yourself, and how to take notes during a call without anyone seeing compares it fairly with presenter view, a second monitor and paper, since one of those may suit you better.
HushNotes uses that property for every note window, on by default. It is Apple's mechanism rather than ours, so treat it as a strong privacy measure and not a guarantee, and check it against your own setup before a call that matters. The feature page for screen-share privacy shows the same desk captured twice, once as its owner sees it and once as a share sees it.
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