How to install

What you need before you start

• The computer you want to reach, switched on, with you standing at it. Pairing is physical, so this part cannot be done remotely.
• The TETHERÆ app on your phone or tablet.
• An account. One account covers every machine you pair.

The agent is what runs on the computer. The app on your phone connects to it. You install the agent once per machine.

Windows

1. Download and check the file

Take the 64-bit installer unless you know the machine runs a 32-bit edition of Windows. To check: Settings, System, About, and read System type.

Before running it, confirm the file you received is the file we published. Open Command Prompt in your Downloads folder and run this. The output must match the value below it, ignoring the spaces Windows prints.

2. Run it, past the blue box

Windows will show a blue “Windows protected your PC” panel, and the elevation prompt will say the publisher is unknown. That is SmartScreen reacting to an installer it has not seen signed before. It is not a scan result and it is not a virus report. This installer is not code signed yet, so every user sees it.

• Click More info.
• Click Run anyway.
• Approve the elevation prompt. It appears because the agent installs as a Windows service.

3. What it installed

• A Windows service called TetherAgent, which is what makes the machine reachable again after a restart, without anyone logging in.
• The Tether app, for pairing and for granting control.
• Two inbound firewall rules, both named Tether: TCP 47810 and UDP 47811, for direct connections on your own network. Connections from outside your network go out through the relay and need no rule.
• A registry policy that lets the service send Ctrl+Alt+Del, so you can sign in to a locked machine rather than only look at it.

4. Giving it full access, and checking it took

The installer does all of this for you. These commands are here so you can verify it, and repair it if a security product or a group policy has undone something. Open Command Prompt as Administrator: press Start, type cmd, then right click Command Prompt and choose Run as administrator.

5. If it installs but will not run

Two causes account for nearly all of it, and neither is fixed by reinstalling.

An N or KN edition of Windows. These ship without Media Foundation, which the agent needs to encode video, so the service fails at start rather than at install. Check which edition you have, and if the answer ends in N, install the Media Feature Pack from Windows Update, under Optional features.

Windows older than 10 version 1809. The installer is more permissive than the program, so an older machine can install it and then fail to run it. There is no fix other than a newer Windows.

If neither applies, read the service’s own log of why it stopped.

6. Removing it

Settings, Apps, Installed apps, then Tether, then Uninstall. Or from an Administrator Command Prompt, pointing at the same installer you ran:

macOS

1. Download and check the file

The Mac download is a disk image containing two applications: Tether Agent, which is what makes this Mac reachable, and Tether, which lets this Mac control another one. You need the agent. Install both if you want the Mac to work in either direction.

2. Install it

Open the disk image and drag both applications into Applications. Then open Tether Agent.

The Mac build is signed and notarized by Apple, so it opens without a warning. If you want to see that for yourself rather than take our word for it:

It should answer accepted, source=Notarized Developer ID, and name ABIOMYE INDUSTRIES PRIVATE LIMITED. If macOS ever refuses to open it because the file was copied through something that stamped it as quarantined, clear that stamp:

3. Giving it full access

macOS will not let any program see your screen or move your pointer until you say so, and it asks separately for each. The agent needs both, and it is useless without them: without Screen Recording you get a black picture, without Accessibility you get a picture you cannot touch.

The agent asks for these itself the first time it runs. These commands open the exact panes, for when you dismissed the prompt or want to check the state.

Quit and reopen Tether Agent after granting Screen Recording. macOS only hands the permission to a program when it next launches, which is why a freshly ticked box often appears to do nothing.

If a switch is stuck, or the agent still says a permission is missing after you granted it, reset the decision and let it ask again. This is a known macOS behaviour after an application is replaced by a new version.

4. Make it start when the Mac starts

This is the one real difference between the platforms, and it is worth knowing. On Windows the agent is a service, so the machine is reachable after a restart with nobody logged in. On macOS it is an ordinary application: it does not add itself to your login items, so after a restart it is not running and the Mac is not reachable until you open it.

Add it yourself if you want the Mac to come back on its own after a restart. It still only starts once somebody logs in, because that is how macOS works.

5. Checking it is running

6. Removing it

Drag both applications from Applications to the Bin. Then clear the permissions you granted, so nothing is left holding a decision about a program that is gone:

Linux

Install the package for your architecture. Use amd64 on an ordinary PC and arm64 on a Raspberry Pi or an ARM server.

The agent runs as a user service, not a system one, because it needs your graphical session in order to see your screen. That means it starts when you log in.

Pairing your phone

With the agent running, open Tether on the computer. It shows a QR code. Open the app on your phone, tap Pair a machine, and point the camera at that code. That is the whole setup.

Pairing is done by somebody standing at the machine, on purpose. There is no ID number to read out over the phone and no session request to accept. If somebody claiming to be from your bank, Apple or Microsoft asks you to install remote access software so they can help, hang up. That attack does not work here, because adding a machine requires being at it.

If the camera cannot get a clean read, tap Enter code manually and type the code shown under the QR.

If a connection will not establish

• Both on the same Wi-Fi and it still will not connect. Something is blocking TCP 47810 or UDP 47811 on the computer. Check the firewall commands above. The connection falls back to the relay, so it should still work, just with more latency.
• Works at home, not elsewhere. That is the relay path, and it needs nothing opened on your router. If it fails, the agent is probably not running: check the service on Windows, or that the app is open on macOS.
• The picture is black. On macOS, Screen Recording was granted but the agent was not restarted. Quit it and open it again.
• The picture is fine but nothing responds to touch. On macOS, Accessibility has not been granted.
• Everything worked, then went black after using Rest. Update the agent. That was a real fault in earlier builds and it is fixed in the current one.