OpenDisplay turns iPhone, iPad or spare Mac into a Mac external display

OpenDisplay, a free open-source application that turns an iPhone, iPad or another Mac into an external display for a Mac, has been presented as an alternative to paid tools such as Apple Sidecar, Duet Display and Luna Display, according to gigazine.net.

The software pairs a Sender app installed on the Mac with a Receiver app on the iPhone or iPad, and connects over USB or Wi-Fi. It extends the Mac desktop instead of mirroring it, supports Retina resolution and accepts touch input including tap, click, drag and two-finger scroll.

A single Mac can drive up to three iPhone or iPad devices at once, mixing iPad and iPhone. Over USB the app supports HiDPI (@2x) rendering at up to 60FPS and can charge the connected device while it is in use; Wi-Fi connections are set up through Bonjour automatic discovery. No subscription, dongle or account registration is required, and no Apple Account or login is needed.

Devices communicate only through direct TCP connections, with no servers or telemetry, according to the project. A Receiver app supporting macOS 12 or later also allows an old Mac to serve as a second display, and a portrait mode turns a device into a vertically oriented virtual display.

Unlike Apple Sidecar, OpenDisplay supports the iPhone as a display and pairing between devices signed in to different Apple Accounts. The official clients are the Mac Sender and the iOS/iPadOS Receiver, with third-party Android Receiver, legacy iOS 12 Receiver and Linux Sender clients also available. The project is developed individually by Philipp Poloczek, who lives in Germany.