EternalMonitor

Mirror or extend your Windows desktop onto an iPad over Wi-Fi or USB,
and control the PC with touch, a keyboard or Apple Pencil.

Download · Setup guide · Website · Release notes

EternalMonitor streams your Windows desktop to an iPad and sends your input back. A small Windows app captures the screen and encodes it on your graphics card. The iPad app decodes the video in hardware and draws it with Metal, and every tap, keystroke and Pencil stroke travels back to the PC. It is free, open source under the MIT license, and needs no account.

• Extend or mirror. Add the iPad as an extra display beside your monitor, or mirror any screen you have. The extra display exists only while the iPad is connected, so Windows never keeps a phantom monitor around.
• Wi-Fi or USB. Stream over your home network, or plug in a cable for a steadier picture that also charges the iPad. A cable takes over a running Wi-Fi session, and unplugging it falls back to Wi-Fi.
• Touch, keyboard and pointer. Tap to click, drag, scroll with two fingers and hold to right-click. Hardware keyboards, trackpads and mice work too, with sticky modifiers and middle-click.
• Apple Pencil as a real pen. Windows receives Windows Ink pressure and tilt. Drawing mode ignores your palm on the canvas, and Clip Studio Paint works with its Tablet PC setting.
• PC audio. Sound plays on the iPad as Opus, with a jitter buffer and loss concealment. You can mute it without stopping the video.
• Loss repair for real Wi-Fi. When a packet goes missing, the iPad asks for that fragment again right away, so one dropped packet rarely costs a frame. The bitrate adapts between 4 and 50 Mbps.
• Your GPU does the work. NVIDIA NVENC, AMD AMF or Intel Quick Sync encode H.264 by default, or HEVC if you prefer it, at 30, 60, 90 or 120 fps.
• Pairing. The first Wi-Fi connection asks for a six-digit code or a QR scan. After that the iPad remembers the PC. USB needs no code.

Install both apps from the same version. The older v0.1 releases use a different protocol and cannot connect to the v0.3 iPad app.

Testing it? Send bugs and feedback through the form on the download page, which emails hello@sideband.studio, or open a GitHub issue.

The installer is not code-signed yet, so Windows SmartScreen asks before it runs. Choose More info, then Run anyway, only after checking that the file's SHA-256 matches the one on the release page.

For USB you also need Apple's free Apple Devices app, open while you stream. Windows can only reach an iPad over a cable through it, and EternalMonitor tells you when it is closed or missing.

Next, follow the setup guide. It walks through installing both apps, pairing, USB, the extended display and drawing, with the exact button names you will see.

v0.3.0 is the current stable release, paired with iPad TestFlight build 143. Its Windows installer is unchanged from v0.3.0-rc.1. On 2026-09-24 it passed the automated tests on a reference PC with GeForce RTX 5080 and Radeon graphics and on a physical iPad Pro. Those included 30-minute runs at about 58 fps, one over Wi-Fi at 3440×1440 and one over USB at 2732×2048. Testers are now checking what needs hands on the device, such as drawing in Clip Studio Paint and audio sync. docs/hardware-verification.md has every result, including the failures.

Known limits:

• The stream is not encrypted. Pairing keeps other devices out, so use a network you trust, such as your home Wi-Fi.
• The Windows app is the only host. The host builds on macOS for development, but there it streams a test pattern instead of your screen.
• Apple Pencil (USB-C) has no pressure sensor, so its strokes keep one width.

flowchart RL
  subgraph pc [Windows PC]
    direction TB
    capture[Desktop capture] --> encode[GPU encoder]
    inject[Input injection]
  end
  subgraph ipad [iPad]
    direction TB
    repair[Reassembly and repair] --> decode[VideoToolbox decode] --> show[Metal display]
    touch[Touch, keyboard, Pencil]
  end
  pc -- "video and audio over Wi-Fi or USB" --> ipad
  ipad -- "input and repair requests" --> pc

The Windows host is written in Rust. It captures the desktop with DXGI, encodes on the GPU through FFmpeg, and sends each frame as numbered UDP fragments. Over USB the same messages travel through a framed tunnel that Apple's device service provides. The iPad app is native Swift. It reassembles fragments, requests any that are missing, decodes with VideoToolbox and renders with Metal. Input and receiver reports go back on the same session, and the host uses those reports to adapt the bitrate.

ARCHITECTURE.md describes the pipeline and protocol v2, and docs/decisions.md explains why each part works the way it does.

The workspace holds the Rust host (host/), the protocol crate eternal-wire (proto/) and the Swift iPad app (ios/).

# Point the build at your FFmpeg 7.1 shared SDK (the folder with bin\avcodec-*.dll)
$env:FFMPEG_DIR = "C:\ffmpeg"
cargo build --release -p eternal-host
.\target\release\eternal-host.exe          # optional port argument, default 9876

brew install ffmpeg@7 pkgconf xcodegen
export PKG_CONFIG_PATH=/opt/homebrew/opt/ffmpeg@7/lib/pkgconfig
cargo test --workspace          # unit, golden-vector and synthetic end-to-end tests
ETERNAL_CAPTURE=synthetic cargo run -p eternal-host

cd ios
xcodegen generate               # project.yml is the source of truth
xcodebuild test -project EternalMonitor.xcodeproj -scheme EternalMonitor \
  -destination 'platform=iOS Simulator,name=iPad Pro 11-inch (M4)'

./scripts/e2e_ios.sh              # synthetic host to the iPad simulator, H.264
EM_CODEC=hevc ./scripts/e2e_ios.sh
scripts/test_ios.sh               # iPad unit and UI tests
scripts/e2e_matrix.sh             # UDP, loss, burst, USB, audio, pairing, input, lifecycle
scripts/soak.sh 1800              # 30-minute frame-rate and memory check

Contributions are welcome, from transport and encoders to rendering and docs. Read CONTRIBUTING.md before opening a pull request. To talk an idea through first, message aldobenches285 on Discord.

Found a bug? Open an issue with both app versions and the host log. Report security problems privately as described in SECURITY.md.

EternalMonitor is released under the MIT License, © 2026 Ali Younes. The Windows installer also ships third-party components under their own licenses, including the Virtual Display Driver and FFmpeg.

Built by Ali Younes (@whoisaldo). Questions go to hello@sideband.studio.