How to Resolve: Slack Camera “In Use by Another Application”

When Slack displays a “Camera in use by another application” error, the app cannot capture video during Huddles, calls, or video clips because the hardware interface is locked. Most operating systems grant exclusive hardware control to one process at a time. If a background conferencing tool, browser tab, or virtual camera driver retains an active handle on the sensor, Slack is blocked from streaming video.

Fast Fix

Close all background applications that use your webcam, such as Zoom, Microsoft Teams, Google Meet browser tabs, OBS Studio, or FaceTime. Then open Slack, toggle your video off and on, or restart Slack completely to allow it to claim the newly released video capture interface.

Diagnostic Snapshot

Parameter	Diagnostic Details
Error Message	“Camera in use by another application” or black video preview
Affected Surface	Slack Desktop Client (Windows / macOS) and Slack Web
Root Cause	Exclusive hardware lock by background process, hung driver process, or virtual video filter
Access Level	Standard User (Local OS Settings & Task Manager)

Isolating the Lock Source

Before adjusting system drivers, isolate which process or layer holds the hardware stream.

Is the camera failing only in Slack or across all system apps?
 ├── Only fails in Slack
 │    ├── Check Slack Preferences > Audio & Video: Is a virtual camera (OBS/Logi Tune) selected?
 │    └── Check Slack OS permissions: Is desktop camera access enabled for Slack?
 └── Fails across all apps (e.g., Windows Camera App / macOS Photo Booth)
      ├── Process lock: A background service (Teams/Zoom/Chrome) is running invisibly.
      └── Driver crash: The camera controller service (Frame Server on Windows / VDCAssistant on macOS) has hung.

What Causes the Camera Conflict

Webcam hardware drivers communicate with operating systems via standard media pipelines (DirectShow and Media Foundation on Windows; AVFoundation and CoreMedia on macOS). When an application requests a video stream, the system creates an active session handle.

If an application fails to release the session handle when minimized, or if a background service runs with active capture listeners, the kernel rejects Slack’s subsequent connection request. Common sources of this lock include:

• Zombie Video Processes: Background instances of conferencing apps (Zoom, Teams, Discord) remaining in memory after closing their main window.
• Open Browser Tabs: Web apps (such as Google Meet, Loom, or web conferencing portals) actively maintaining media stream permissions.
• Virtual Camera & Filter Drivers: Virtual devices like OBS Virtual Camera, Camo, or manufacturer utilities (Logitech G HUB, Logi Tune, Elgato Camera Hub) intercepting the native video feed.
• Corrupted Driver Pipelines: The underlying OS camera background daemon becoming unresponsive without notifying the desktop environment.

Step-by-Step Resolution

1. Terminate Background Video Processes

Ensure no other application is holding an active capture stream.

• Windows 11 / 10:
  1. Press Ctrl + Shift + Esc to open Task Manager.
  2. Inspect the Processes tab for background tasks: Zoom.exe, Teams.exe, Discord.exe, or chrome.exe.
  3. Select the conflicting process and click End Task.
• macOS:
  1. Open Activity Monitor via Spotlight (Cmd + Space).
  2. Search for Zoom, FaceTime, Teams, or VDCAssistant.
  3. Select the process and click the Stop (X) button > Force Quit.

2. Reset the Operating System Camera Daemon

If no visible apps are running, the background camera daemon may be hung in an active state. Restarting this service clears ghost handles without requiring a system reboot.

• On macOS: Open Terminal and enter: Bash sudo killall VDCAssistant sudo killall AppleCameraAssistant (Press Enter and input your administrator password. The daemon will automatically restart cleanly).
• On Windows:
  1. Press Win + R, type services.msc, and press Enter.
  2. Locate Windows Camera Frame Server.
  3. Right-click the service and select Restart.

3. Verify Video Device Selection in Slack

Slack may default to an inactive virtual camera driver rather than your physical webcam.

1. In Slack, click your profile picture and select Preferences (Cmd + , on Mac or Ctrl + , on Windows).
2. Navigate to Audio & Video.
3. Scroll to Camera and check the dropdown menu.
4. If a virtual driver (e.g., OBS Virtual Camera, Logi Capture) is selected, change it directly to your integrated webcam or dedicated USB camera.
5. If the video screen flickers or turns solid green when switching devices, refer to Slack Huddle “Green Screen” or Flickering Video.

4. Confirm OS-Level Privacy and App Access

If the operating system revokes hardware access while a call is initiating, Slack may misinterpret the permission drop as another program blocking the device.

• macOS: Navigate to System Settings > Privacy & Security > Camera. Verify that Slack is toggled to On.
• Windows: Go to Settings > Privacy & security > Camera. Ensure Camera access and Let desktop apps access your camera are toggled on. If permissions loop or fail to apply, review “Microphone Access Denied” by Windows Privacy Settings for related system permission fixes.

Common Misdiagnoses

• Hardware Acceleration Glitches: If Slack displays a solid black screen rather than an explicit “in use” notification, the issue may be hardware decoding failure rather than a device lock.
• Virtual Background Processing Halts: If the camera feed fails only when enabling background effects or blur, see Troubleshooting: Slack Huddle “Background Blur” crashing Chrome or “Virtual Backgrounds” not loading in Slack App.
• Network Signaling Timeouts: If the entire Huddle fails to start when toggling video, the underlying WebRTC handshake may have timed out. Refer to “Failed to start Huddle” (Error Code: 1001).

When to Check Hardware Connections

If you have terminated conflicting applications and reset system camera daemons but the camera remains unavailable:

• USB Hub Bandwidth Saturation: High-definition USB webcams connected through unpowered USB splitters or multi-port docks may fail to negotiate video bandwidth when external drives or monitors are active on the same bus. Connect the webcam directly to a dedicated motherboard USB port.
• Physical Shutter Switches: Many modern webcams and laptop bezels feature mechanical privacy sliders or electrical kill switches. Ensure the physical sensor shutter is fully open, as some sensors report an active bus lock to the OS when closed.