Screenjack

A monitor app for Mac and iPad

Plug it in.
Your Mac or iPad is the monitor.

Plug an inexpensive HDMI-to-USB capture device into your Mac or a USB-C iPad, plug your console, camera or board into that, and Screenjack shows the picture full screen with sound. If it has HDMI out, it fits on your screen.

Download on the App Store
  • macOS 14 or iPadOS 17
  • Sandboxed
  • Records nothing

It needs a small capture device. See what to buy

Screenjack full screen on a Mac, showing the desktop of a single-board computer. The control bar along the bottom holds the capture device menu, the Fit, Fill, Stretch and Pixel-perfect modes, a volume slider, and a full screen button.

What you need

Four things and one cable path.

Screenjack is software. The picture comes in through a small, inexpensive HDMI-to-USB capture device that plugs into your Mac or a USB-C iPad. Here is the whole chain, and every device on the wheel works the same way.

Your deviceGame console

You already own it

HDMI cablenothing special

The cable you have

Capture deviceHDMI in, USB out

The one thing to buy

Your Mac or iPadmacOS 14 or iPadOS 17, USB or USB-C

Screenjack runs here

  1. A source with HDMI out

    Game console, docked handheld, single-board computer, laptop, camera, mini PC, or a streaming box that is not copy-protected.

  2. An HDMI cable

    Nothing special. The cable that came with the device is fine.

  3. An HDMI-to-USB capture device

    A small adapter with HDMI in and USB out, sold everywhere for not much. Up to 1080p at 60 fps with a USB 3.0 capture device. USB 2.0 models cost less, trade a little resolution or frame rate, and are fine for most uses.

  4. A Mac or a USB-C iPad

    A Mac on macOS 14 or later with a USB port, or a USB-C iPad on iPadOS 17 or later. A USB-C adapter or hub is fine on the Mac.

Capture device
Any HDMI-to-USB capture device that your Mac or iPad sees as a camera. No brand or model is required, and you do not need an expensive one. Up to 1080p at 60 fps with a USB 3.0 capture device. USB 2.0 models cost less, trade a little resolution or frame rate, and are fine for most uses.
Mac or iPad
A Mac on macOS 14 or later with a free USB port, or a USB-C iPad on iPadOS 17 or later. A USB-C adapter or hub is fine on the Mac.
HDCP
Copy-protected sources show a black picture. That protection is on by default on some game consoles and most streaming boxes. Game consoles usually let you turn it off in their video or HDMI settings; streaming boxes and protected video apps generally do not.
Audio
Sound plays through your Mac or iPad. Bluetooth headphones and speakers add a noticeable delay of their own, so use wired output or the built-in speakers for gaming.

What it does

A monitor, and nothing else.

No recording, no snapshots, no filters, no streaming, no accounts, no network. Screenjack draws the picture, plays the sound, and stays out of the way.

The Screenjack window in Pixel-perfect mode: the 1080p desktop of a single-board computer drawn at whole-number scale with black around it, and the control bar below.
Pixel-perfect. Whole-number scaling with no smoothing, black around the picture, and the window title showing the device, resolution, and frame rate.
Screenjack's Settings window on the Audio tab: Play audio from the capture device, Swap left and right channels, Fix mono 96 kHz audio set to Auto, and Audio device set to Auto (paired).
Audio settings. Passthrough on or off, left and right swap, the automatic fix for inexpensive sticks, and which input to pair.
The Screenjack window showing the built-in test pattern: seven color bars over a dark field with the resolution and frame rate printed in the corner.
Test pattern. Try every control before your capture device arrives. It is in the Help menu on the Mac, or on the iPad start screen.

Straight to the screen

Frames go from the capture device to a Metal layer and are drawn as they arrive. Late frames are dropped, never queued.

Four ways to fit

Fit, Fill, Stretch, and Pixel-perfect: whole-number scaling with no smoothing, made for retro consoles and low-resolution boards.

Sound that works

Audio passes straight through with a small buffer. Inexpensive USB 2.0 sticks that report the wrong format are fixed automatically, and you can swap left and right by hand.

Plug and unplug freely

Devices appear as you connect them. Your last device reconnects on its own, and unplugging shows a clear message instead of a frozen frame.

A clean canvas

Pure black around the picture. The controls appear on demand and fade on their own. On the Mac the pointer hides over live video, with Float on Top and Lock Window to Aspect; on iPad the picture is always full screen.

Awake while it matters

Your Mac or iPad stays awake while video is showing, and rendering pauses when the picture is covered.

Format control

Auto picks the best format your capture device offers, or choose one yourself, remembered per device model. Color range Auto, Limited, or Full.

Try it without hardware

A built-in test pattern lets you explore the app before your capture device arrives, on the Mac or on iPad.

Keyboard on the Mac

  • Full Screen⌃⌘F
  • Fit, Fill, Stretch, Pixel-perfect⌘1 to ⌘4
  • Float on Top⌘⇧T
  • Lock Window to Aspect⌘⇧L
  • Next Device⌘]
  • Mute⌘⇧M
  • Volume up and down⌘↑ ⌘↓
  • Settings⌘,

Who plugs in

One spare screen, five kinds of people.

Screenjack full screen on a Mac, showing a game from a console: a top-down battle arena with a match timer, a minimap, and an ability bar, and the Screenjack control bar along the bottom edge of the display.
A console on the Mac's display. Full screen, with the controls showing for a moment after the mouse moved.
Screenjack showing a camera's live view: five people posing in front of a white studio backdrop, with the camera's own framing brackets, record light, battery, and timecode drawn over the picture.
A camera's live view, big and clean. The framing marks and record light come from the camera. Screenjack draws nothing on top.

Gamers

Play a console or a docked handheld on your Mac or iPad. Retro consoles at pixel-perfect scale, with stereo audio that works.

Photographers and filmmakers

A big, clean live view for a camera with HDMI out. Framing, focus, and a screen you can turn toward a client.

Makers and tinkerers

Set up and debug a single-board computer, a mini PC, or a headless box without a spare monitor. Boot screens show too, because it is plain HDMI.

Anyone short a monitor

A second laptop or device on a small desk, in a hotel room, or anywhere a spare display is not an option. On iPad it travels in a bag.

Streamers and presenters

A clean preview of a second device, with nothing drawn on top of the picture.

Permissions, honestly

It will ask for the camera. Here is why.

macOS and iPadOS treat a capture device as a camera, and its audio as a microphone. That is the only way any app can read the signal, so Screenjack asks for exactly those two permissions, each at the moment it needs it.

  • Nothing is recorded
  • No network access
  • Sandboxed
  • No analytics in the app

Camera

Asked
The first time a capture device connects, after a short explanation of why.
Used for
Seeing the video coming in over HDMI so it can be drawn on your screen.
Stored
Nothing. Frames are drawn and discarded.

Microphone

Asked
Only once video is live, and only if audio is switched on.
Used for
Hearing the capture device's audio so your Mac or iPad can play it.
Stored
Nothing. Audio is played and discarded.

Entitlements: sandbox, camera, audio input. That is the full list.

Good questions

Before you plug in

Why is the picture black?

Almost always because the source is copy-protected (HDCP). Screenjack shows a hint when it sees this. Game consoles usually let you turn HDCP off in their video or HDMI settings. Streaming boxes and protected video apps generally do not, and those will stay black. If HDCP is off and it is still black, lower the source's resolution or refresh rate; see Help.

Which capture device should I buy?

Any HDMI-to-USB capture device that your Mac or iPad sees as a camera. Up to 1080p at 60 fps with a USB 3.0 capture device. USB 2.0 models cost less, trade a little resolution or frame rate, and are fine for most uses. We do not recommend specific models, and you do not need an expensive one.

Is the sound delayed over Bluetooth?

Bluetooth headphones and speakers add a noticeable audio delay of their own, which no app can remove. For gaming, wired output or the built-in speakers keep the sound in step with the picture.

Does it record anything?

No. Screenjack shows the picture and plays the sound, and that is all. There is no recording, no snapshots, no streaming, no filters, and no network access.

Can I try it before my capture device arrives?

Yes. Open the built-in test pattern (the Help menu on the Mac, or the button on the start screen on iPad) to explore the window, the aspect modes, and the controls without any hardware.

Which Macs and iPads does it run on?

Any Mac on macOS 14 or later with a free USB port, or a USB-C iPad on iPadOS 17 or later. A USB-C adapter or hub works fine on the Mac.

How is Screenjack different on iPad?

It is the same app and the same picture. The iPad needs a USB-C model on iPadOS 17 or later, the controls are by touch instead of the keyboard, and the picture is always full screen. Everything else, including the aspect modes and audio, works the same way. On the entry-level iPad, whose USB-C port runs at USB 2.0 speed, expect a little less resolution or frame rate than a Mac gets from the same capture device.

Your next monitor is already on your desk.

Screenjack is one app for Mac and iPad, on macOS 14 or iPadOS 17 or later. Add a small capture device, and it shows anything with HDMI out, sound included.

Download on the App Store