WinSync mirrors your Windows system audio to a second output device — wired, Bluetooth, or USB — with per-device delay and drift correction, so nothing goes stale or drifts apart over a two-hour movie.
Windows 10/11 · MSI installer, ~700KB · free & open source
Windows routes system audio to one output at a time. There's no built-in way for two people to share one laptop through two pairs of headphones — until now.
Wired + Bluetooth is the common case, but any two WASAPI output devices work.
Bluetooth adds 150–250ms of latency. A slider lets you compensate exactly.
Two devices never share a clock. A continuous ±0.3% speed nudge keeps them locked for hours, with no clicks.
Pure user-mode WASAPI loopback. No kernel driver, no code-signing certificate, no elevation prompt.
Tap one endpoint with WASAPI loopback capture, re-render the stream to any number of others.
The key trick: loopback capture happens inside the Windows audio engine, before the signal reaches the Bluetooth radio — so the captured copy is never delayed by Bluetooth. Tap the slowest device, delay the faster one to catch up. Read the full design writeup →
Wired + Bluetooth setup, the most common case:
1. Connect both headphones.
2. Set the Bluetooth headphone as the Windows default output.
3. In WinSync, set Tap device to that same Bluetooth headphone.
4. Set Output 1 to the wired headphone.
5. Press Start, play a video, drag Delay until they line up (usually 120–250ms).Full instructions, known limitations and troubleshooting are in the README.