Fix a silent streaming app in the Windows volume mixer
Keep the app playing while you check its individual volume and output. System sounds may already be using a different route.
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Open the mixer while the app is playing
In Windows Sound settings, open Volume mixer while the affected player or browser has a video running. Check the app entry for mute and volume, then inspect its selected output. Change it to the intended display, headphones or speakers. A system alert sounding through your headphones gives you no assurance that a browser tab is following the same output setting.
Repeat with a familiar audio track
Test a second title with ordinary stereo audio. If only one programme stays silent, choose another available track inside the player and check the browser tab mute state. If the app keeps selecting an old Bluetooth device, set the intended output and restart that app once. Record whether other apps can use the same output before changing audio drivers.