What is capture exclusion, and which words describe it?
Capture exclusion is an operating-system feature that leaves one window out of screen shares, recordings and screenshots made through capture paths that honour it, while the window stays visible on your own display. It is documented on Windows and inconsistent on current macOS. It hides a window from capture software, not from people, cameras or other programs.
- Capture exclusion
- Capture exclusion is a per-window flag that asks the operating system to leave that window out of screen capture. Microsoft documents it for Windows 10 version 2004 and newer; on macOS the flag is legacy, and newer capture paths such as ScreenCaptureKit may capture the window anyway. The explainer on how capture exclusion works covers the mechanism.
- Content protection
- Content protection is the name Electron and several apps use for the same idea: a window flagged so capture software leaves it out. In Electron the switch is
setContentProtection. Despite the name, it is not DRM. Microsoft states that display affinity gives no security guarantee, for example against a photograph of the screen. - “Invisible” vs “undetectable”
- “Invisible to screen recording” is shorthand for capture exclusion, and it is only true for supported capture paths. “Undetectable” claims that no person, tool or method can notice the assistant, which no operating-system feature supports, so Kopya never uses the word. The invisible AI overlay definition compares the two claims side by side.
- Supported capture path
- A supported capture path is a capture method that honours the exclusion flag. Microsoft says only a specific set of operating-system features and APIs honour display affinity, and Electron documents that macOS apps capturing through ScreenCaptureKit do not. “Supported” in Kopya’s copy always means this. The compatibility page lists what each vendor documents for its own tool.
Which APIs do apps use to hide a window from screen capture?
Apps use two layers: a framework call such as Electron’s setContentProtection, and the operating-system API it maps to underneath, SetWindowDisplayAffinity with WDA_EXCLUDEFROMCAPTURE on Windows and NSWindow.sharingType = .none on macOS. The entries below define each name briefly; the developer explainer walks through them with code samples.
setContentProtectionsetContentProtection(enable)is the ElectronBrowserWindowmethod that turns capture exclusion on or off for one window. Electron’s documentation says it usesWDA_EXCLUDEFROMCAPTUREon Windows andNSWindowSharingNoneon macOS, and warns that macOS apps capturing through ScreenCaptureKit capture the window anyway. Kopya calls this method on its panel.SetWindowDisplayAffinitySetWindowDisplayAffinityis the Win32 function that sets a top-level window’s display affinity: where its pixels are allowed to appear. Per Microsoft’s documentation, the window must belong to the calling process and the setting works only while the Desktop Window Manager is composing the desktop. See the Windows guide.WDA_EXCLUDEFROMCAPTUREWDA_EXCLUDEFROMCAPTUREis the display-affinity value that removes a window from captures. Microsoft says the window is displayed only on a monitor and “Everywhere else, the window does not appear at all”. It arrived in Windows 10 version 2004 (build 19041); on older builds Windows treats it asWDA_MONITOR. Microsoft’s own example use is hiding recording controls from a recording.WDA_MONITORWDA_MONITORis the older display-affinity value. The window is shown on the monitor, but everywhere else it appears with no content, so captures show a blank or black rectangle where the window sits. It is the fallback on Windows builds older than 19041, and the reason some apps “go black” in a share instead of disappearing.GetWindowDisplayAffinityGetWindowDisplayAffinityis the Win32 function that reads a window’s display-affinity setting. Microsoft notes that it works from any process, so other software can tell that a window is flagged. Capture exclusion therefore hides pixels, not the fact that a window asked to be excluded.NSWindow.sharingTypeNSWindow.sharingTypeis the AppKit property that governs whether a macOS window’s content may be read by other processes. Capture exclusion sets it to.none. Apple’s documentation now calls.nonea legacy constant and says not to use it to hide content from capture. See what works on a Mac now.- ScreenCaptureKit
- ScreenCaptureKit is Apple’s modern framework for capturing screen content on macOS. Apps built on it have been reported to capture windows flagged with
sharingType = .none, and Electron’s documentation says so directly. Apple’s developer support told a developer in July 2025 that no public API prevents screen capture. Behaviour varies by macOS version and app. - Desktop Window Manager (DWM)
- The Desktop Window Manager is the Windows compositor that draws every window to the screen. Microsoft documents a constraint tied to it: display affinity works only while DWM is composing the desktop. Whether remote-desktop or virtual-machine sessions honour the flag is not documented, so test your own setup before relying on it.
What do overlay, always-on-top and the other window terms mean?
An overlay is a small window that floats above your other apps; always-on-top is the window property that keeps it there. The menu bar (macOS) and system tray (Windows) are where background apps live without a Dock icon or taskbar button. These terms describe how a panel behaves on your display, not whether a capture includes it.
- Overlay
- An overlay is a compact window that sits above other applications so you can read it while working in something else. Kopya’s overlay is a panel at the top centre of the primary display that collapses to a small pill and can be dragged. Overlay describes position and layering; capture exclusion is a separate flag on the same window.
- Always-on-top window
- An always-on-top window is one the operating system keeps above normal windows, including full-screen apps. Kopya’s panel is always on top, stays visible across macOS Spaces, and opens without stealing keyboard focus from the app you are working in. Being on top does not by itself keep a window out of capture; only the exclusion flag does that.
- Primary display
- The primary display is the monitor the operating system treats as the main one. Kopya positions its panel on the primary display and captures only that display when you press the capture hotkey. A second display that you do not share is one of the most dependable ways to keep any window out of a share.
- Panel state label
- The panel state label is the text in Kopya’s panel that reads “Hidden in screen shares” or “Visible in screen shares”. It reports whether the exclusion flag is currently set, not whether a given tool honours it. Read the label first, then run the self-test in the tool you plan to use.
How do screen sharing, screen recording and screenshots differ?
Screen sharing streams your screen live to other participants; screen recording saves it to a file; a screenshot is a single frame. All three go through an operating-system capture path, and whether a capture-excluded window appears depends on that path and the share mode you pick. The tutorial recording guide covers the Mac caveat.
- Screen sharing vs screen recording
- Screen sharing sends a live capture of a display, window or tab to other people in a call. Screen recording writes that kind of capture to a video file, locally or in the cloud. Both depend on the tool’s capture path. Kopya has not published per-tool test results, so run the self-test in the exact mode you will use.
- Screenshot
- A screenshot is a single captured frame of a display or window. Whether a capture-excluded window appears depends on the screenshot tool’s capture path: on Windows 11, Signal reports that its protected windows do not appear in screenshots; on macOS, exclusion from screenshots has been reported while recordings differ. Kopya’s own screenshot omits its panel while privacy is on.
- Presenter view
- Presenter view is a slideshow mode that shows your notes and upcoming slides on your screen while the audience sees only the current slide. It is a native way to keep notes private and works alongside a capture-excluded panel. Presenting with Kopya explains the combination and what the audience actually sees.
- Mirrored display and projector
- A mirrored display or projector shows exactly what your monitor shows, because it is a monitor. Capture exclusion acts on capture software, so a capture-excluded panel is visible on a projector, on a mirrored external screen, and to anyone looking at or photographing your screen. Extend the display instead of mirroring it when you present.
Which terms describe the limits of capture exclusion?
Capture exclusion is not a security boundary. Microsoft says display affinity is not a security or DRM feature, Apple calls the macOS flag legacy, and the flag is readable by other processes. The terms below name the specific limits: the black-rectangle fallback, security boundary, process visibility, and the 60-second self-test that checks your own setup.
- Black rectangle fallback
- The black rectangle fallback is what happens on Windows builds older than 19041: the panel is not removed from a capture but replaced by a blank or black box, because the system falls back to
WDA_MONITOR. Kopya warns about this on such builds. Check your build withwinver; the Windows guide shows how. - Security boundary and DRM
- A security boundary is a control that holds against a determined adversary. Capture exclusion is not one: Microsoft says that unlike a security feature or DRM there is no guarantee, for example against a photograph of the screen. Treat the feature as a convenience for presenting, not a protection for secrets.
- Process visibility
- Process visibility means an app still appears in Task Manager or Activity Monitor and in window lists. Capture exclusion applies to the pixels of one window; it does not hide the running process, the sign-in window, or the flag itself. Monitoring or endpoint software that inspects processes is unaffected. Our responsible use page explains why that matters.
- 60-second self-test
- The 60-second self-test is Kopya’s recommended check: confirm the panel says it is hidden, start the exact tool and share mode you will use, then look at what the other side or a playback actually shows. If the panel appears, share a window, move the panel to an unshared display, or close it. Full steps are on the compatibility page.
- Kopya
- Kopya is a desktop AI assistant for macOS and Windows that answers questions about what is on your screen when you press a hotkey; its panel is excluded from supported screen shares and recordings. It does not join calls or record audio, and it captures only the primary display, on demand. Read more about Kopya.
How does Kopya use these terms?
Kopya sets the exclusion flag on one window, its panel, through Electron’s setContentProtection. Everything else about the app is ordinary. The table maps the glossary terms to what Kopya actually does and to the page that covers each in depth, so you can check the claim behind each word. Every page named here is also listed in the guides index.
| Term | What Kopya does | Read more |
|---|---|---|
| Capture exclusion | Sets the flag on the panel only; on by default on every plan | Feature page |
WDA_EXCLUDEFROMCAPTURE | Used on Windows 10 build 19041 or newer and Windows 11; older builds fall back to a black rectangle | Windows guide |
NSWindow.sharingType = .none | Used on macOS 14 or newer; legacy flag, results vary and built-in recording has been reported to show the panel | Mac guide |
| Supported capture path | Only what vendors document is stated; each tool row says “not yet tested by Kopya” | Compatibility |
| Window share | Recommended as the most dependable method, with the panel as a second layer | Five methods |
| Process visibility | Nothing hides the process, tray icon or sign-in window; use is limited by the terms | Responsible use |
Common questions about these terms
Is “excluded from capture” the same as “invisible”?
Only in a narrow sense. A capture-excluded window is invisible to capture software that honours the flag, on supported OS versions. It stays fully visible on your own monitor, on a projector or mirrored display, to a phone camera, and to anyone standing behind you. That is why Kopya always writes “invisible to supported screen recording”, never “invisible” alone.
Why does this glossary define “undetectable” if Kopya never uses the word?
Because the word dominates search results for this topic and people need to know what it would mean. “Undetectable” claims that no person, tool or method can ever notice the assistant. No operating system offers that, the flag itself is readable by other processes, and the word signals concealment rather than privacy. Defining it is the honest way to decline it. The answers page gives the short version.
Does capture exclusion hide the whole app?
No. It hides the pixels of one flagged window. Kopya’s menu-bar or tray icon and its menu, the sign-in window, and the process in Task Manager or Activity Monitor are all ordinary and visible. Monitoring software that inspects processes is unaffected. The exclusion is a presentation convenience, not concealment.
Is capture exclusion something Kopya invented?
No. It is a mainstream operating-system feature. Microsoft’s own example is hiding recording controls, and its Recall guidance tells developers to use the flag to keep content out of snapshots. OBS Studio uses it to hide its own windows from capture, and Signal and KeePassXC use it for screen security. The explainer on how it works lists these precedents with sources.
Where do I check whether my meeting or recording tool honours the flag?
Start with the compatibility page, which lists what each vendor documents and marks each tool as not yet tested by Kopya. Then run the 60-second self-test in the exact tool and share mode you will use, and repeat it after OS or app updates. Your own test on your own machine is the only result that counts.
Sources
- Microsoft Learn — SetWindowDisplayAffinity (WDA_EXCLUDEFROMCAPTURE, WDA_MONITOR, DWM constraint, not a security guarantee)
- Microsoft Learn — GetWindowDisplayAffinity (readable from any process)
- Microsoft Learn — Recall guidance for app developers
- Apple Developer — NSWindow.SharingType.none (legacy constant)
- Apple Developer Forums — Apple developer support on preventing screen capture (July 2025)
- Electron docs — BrowserWindow.setContentProtection and the ScreenCaptureKit caveat
- OBS Studio PR #5698 — hide OBS windows from capture
- Signal blog — Screen security on Windows
- KeePassXC PR #6030 — screen capture protection
- Zoom Support — advanced screen sharing and window filtering
- Google Meet Help — present during a meeting (tab, window, entire screen)