How to control your Mac remotely

1. Install on the Mac

Download the DMG from the Get the app page, drag Mac@Xa into Applications and open it. That is all of it — no VPN, no network configuration, no account. The icon lives in the menu bar, not the Dock.

1. 1

   The first time you open it your Mac refuses. Go to System Settings → Privacy & Security, scroll to Security and click Open Anyway. Once is enough.

2. 2

   Allow Screen Recording when the app asks — or switch it on yourself in System Settings → Privacy & Security → Screen Recording and reopen the app. This is what lets the other machine see the screen.

3. 3

   Allow Accessibility in the entry right next to it — without it the picture arrives but clicks and keystrokes go nowhere.

4. 4

   Choose what this machine is for: Client if it will be controlled, Remote if it is the one you carry. It then shows its 9-digit ID and 6-digit code, and there is nothing more to type in.

2. How the two machines find each other

Nothing for you to do here — the app handles all of it. This section is just so you know what runs underneath.

1. 1

   The Mac at home opens an HTTPS connection to the meeting point and keeps it, much like a browser tab left open. The server issues its 9-digit ID, and the machine proves it owns that ID with an Ed25519 signature.

2. 2

   When you type the ID on the other machine, the server notifies the Mac at home and issues a single-use ticket. Both ends come back holding it, the server splices the two pipes together and from then on only copies bytes.

3. 3

   Before taking the long way round, the controlling machine spends about 300 milliseconds trying a direct connection on the local network. Same house or same office and the picture goes straight across — nothing leaves the building.

4. 4

   All of it travels over port 443, so to a hotel or corporate firewall the session is just an HTTPS connection. On top of that sits a second encryption layer, keyed from your 6-digit code plus an ECDH secret the two machines exchange between themselves.

3. The first connection

The Mac at home shows its two numbers right on the panel; the machine doing the reaching just types them in.

1. 1

   On the Mac at home, choose Client mode. Wait for the indicator to turn connected, then note the 9-digit ID and the 6-digit code.

2. 2

   On the machine you carry, choose Remote mode and add a machine. Type the ID, give it a name you'll recognise, enter the code.

3. 3

   Click the machine to open its window. Mouse, keyboard and clipboard work as usual; ⌘. closes it.

4. 4

   On a weak link, open the app list inside that window and pick a single app — only its window is streamed.

4. The iPhone and iPad build

The app has been submitted to the App Store and is waiting on review; this build carries no VPN. In the meantime you build it from source with Xcode.

1. 1

   Open the iOS project in Xcode and select your signing team under Signing & Capabilities. There is a single macRM target — it carries no VPN and connects through the meeting point.

2. 2

   Enable Developer Mode on the iPhone or iPad, unlock the screen and plug it in.

3. 3

   Build in the Release configuration and install. A Debug build launched without Xcode attached quits immediately.

4. 4

   On first run the app asks for no configuration at all: type the 9-digit ID and 6-digit code of the Mac at home and the screen appears.

5. When something goes wrong

A few common situations and where to look first.