winget install --id=julianmb.OpenWinSidecar -e OpenWinSidecar turns an iPad into a real extra Windows monitor. A virtual display driver extends the desktop, Intel Quick Sync encodes it to HEVC, and Safari shows it with full touch and keyboard input. No client app, no subscription.
I wanted to use my iPad as a second screen for my PC. The options that exist are subscription services, or remote-desktop apps that feel like driving a car through a letterbox. So I built the thing I wanted instead: a Windows virtual display, streamed to Safari on an iPad as hardware-encoded HEVC, with touch and keyboard input going back the other way.
No client app. No account. No subscription. Open a URL in Safari and it works.
There is deliberately no audio. If something plays on the PC, the iPad stays silent.
I would rather show you numbers I actually measured than round ones. These are from an iPad Air on the same Wi-Fi, streaming a 2360×1640 virtual display, with the encoder tuned for fluidity over sharpness:
| Glass-to-glass latency | ~65 ms flat (was ~150 ms with spikes to 1.4 s before tuning) |
| Presented frame rate | 40–46 fps on motion, 60 fps windows on a static desktop |
| Encoder bitrate | ~10 Mbps at 2360×1640 |
| Capture | DirectX Desktop Duplication, GPU-side, with a GDI fallback |
| Codec | HEVC / hevc_qsv, 8-bit or 10-bit |
Two honest caveats:
| Host | Windows 11, Intel GPU with QuickSync (tested on Arc) |
| Client | iPad Air (4th/5th gen) and iPad Pro, Safari |
| Network | Same Wi-Fi, 5 GHz preferred |
| Permissions | Administrator required — the display driver and GPU capture both need it |
It has not been tested on AMD or NVIDIA GPUs, on Windows 10, or on any browser other than Safari. If you try it on something else and it works — or does not — please open an issue. I am one person with one test rig, and community testing on other hardware is genuinely how this gets better.
From winget (recommended):
winget install Julianmb.OpenWinSidecar
Manually: download OpenWinSidecar-Setup-.exe from the
releases page, verify the SHA-256 in the
release notes, and run it. The installer is not code-signed, so SmartScreen will warn — choose
More info → Run anyway after checking the hash.
Then install FFmpeg, which is what drives the hardware encoder:
winget install Gyan.FFmpeg
Without FFmpeg the app still works, but it falls back to JPEG at several times the bitrate, and the dashboard will tell you so.
Launch it, leave the display on, and open the URL it shows (or scan the QR code) in Safari on your iPad. Share → Add to Home Screen gives you a borderless app with no browser chrome — that is the intended way to use it.
> Set an access password from the dashboard before using this on any network you do not fully > control. See SECURITY.md — by default the server is open to your LAN.
git clone https://github.com/julianmb/OpenWinSidecar
cd OpenWinSidecar
dotnet build OpenWinSidecar.slnx
dotnet test tests/OpenWinSidecar.Service.Tests/OpenWinSidecar.Service.Tests.csproj
node --test tests/viewer.runtime.test.cjs
& src\OpenWinSidecar\bin\Debug\net10.0-windows\OpenWinSidecar.exe # run elevated
Requires the .NET 10 SDK and Node (for the viewer tests).
OpenWinSidecar/
├── src/
│ ├── OpenWinSidecar.Core/ # IddCx driver management, display topology, settings
│ ├── OpenWinSidecar.Service/ # capture, HEVC encoding, HTTP/WebSocket server, viewer
│ ├── OpenWinSidecar/ # WPF dashboard + tray app ← start here
│ └── OpenWinSidecar.Cli/ # command-line control
├── drivers/VDD/ # signed IddCx virtual display driver
├── installer/ # Inno Setup script
├── ios/ # optional native Swift client (compiles in CI, unverified)
├── winget/ # winget-pkgs manifests
└── docs/ # architecture, troubleshooting, release operations
The viewer is a single self-contained index.html served from the app — no build step, no
framework, no bundler. It uses WebCodecs, which is why Safari and a secure context matter.
See docs/ for architecture, network and discovery notes, troubleshooting, and how releases work.
Rather than have you find out:
docs/future-work.md tracks all of this, including the things I tried that did not work.
Issues and pull requests are welcome — especially reports from hardware I do not have. See CONTRIBUTING.md for the release process.
GNU Affero General Public License v3.0. See LICENSE.
The viewer links back here under AGPL §13. If you modify it and let others use it over a network, you owe them your source — that is the deal, and I am fine with it.