App-Specific Video & Camera Conflicts
Why Can Only One Application Use My Webcam at a Time?
Most USB webcams follow the USB Video Class (UVC) standard, which is built around a single active streaming session at the hardware and driver level — a genuine physical constraint of the standard itself, not an arbitrary software limitation any particular app could simply remove. Virtual camera drivers work around this by having one real application hold the physical camera exclusively, then re-broadcasting that feed to a separate virtual device that other applications can each connect to independently.
Hardware and Kernel Restrictions on Direct Media Streams
This single-connection restriction traces back to how UVC cameras are actually designed at the firmware level — the camera's own internal hardware manages one video pipeline at a time, streaming to whichever single application currently holds it, rather than internally splitting its output to multiple simultaneous recipients the way some other kinds of hardware can.
Operating systems enforce this consistently, since it reflects a genuine hardware constraint rather than an OS policy choice — Windows, macOS, and Linux all handle standard UVC cameras the same fundamental way, denying a second application's request while a first one already holds an active connection, regardless of which specific OS or driver is involved.
This matters practically any time you want to use one physical camera in more than one place at once — streaming software and a separate call app, or two different call apps simultaneously — since the hardware itself simply isn't built to support that directly, no matter how the software side is configured.
How Virtual Camera Drivers Bypass Single-App Locks
Virtual camera software solves this by inserting itself as an intermediary: one real application (commonly OBS, though other tools work similarly) holds the actual physical camera exclusively, exactly as the hardware requires, then creates and continuously feeds a separate virtual video device that any number of other applications can each connect to independently, since a virtual device isn't bound by the same single-client hardware constraint a real physical camera has.
From every other application's perspective, this virtual device looks and behaves exactly like a normal camera in every practical way — it appears in device lists, can be selected the same way, and streams video normally — the fact that its source is actually a re-broadcast of a physical camera rather than direct hardware access is invisible to whatever's consuming it. ↑ Test any virtual camera setup you build with the widget above.
Some Newer Cameras Are an Exception
It's worth knowing this single-client limitation isn't strictly universal across every camera ever made — some newer, higher-end cameras and certain specialized capture hardware do support multiple simultaneous streams at the hardware level. For the overwhelming majority of consumer USB webcams most people actually own, though, the single-client UVC pattern described here is what determines real-world behavior, and it's the safest assumption to plan around unless you've specifically confirmed otherwise for your exact hardware.
Built-in laptop cameras follow this same single-client pattern just as consistently as external USB webcams, since they're typically also implemented as UVC-compliant devices internally, connected via an internal USB bus rather than an external port.