A shared Mac rejects the VNC password from Linux or Windows

You click a shared Mac in Remote Machines, the VNC client opens and reaches the Mac, but the password is refused (or the client reports an authentication failure) — even though it's correct.

What it means

macOS Remote Management only accepts standard VNC password authentication from third-party clients (Remmina, TightVNC, RealVNC and the like) once that's explicitly turned on. Until then the Mac expects Apple's own authentication, which only another Mac speaks. Reach's tunnel is fine — the VNC handshake reached the Mac; it's the Mac's authentication setting that's blocking you.

Fix

On the Mac being shared:

  1. Open System Settings → General → Sharing.
  2. Next to Remote Management, open the settings (the ⓘ button) → Computer Settings…
  3. Tick "VNC viewers may control screen with password" and set a VNC password.
  4. Reconnect from Linux or Windows and enter that VNC password (not the Mac user's login password).

Common questions

The Mac isn't listed in Remote Machines at all

Sharing must be on and you must be an authorised viewer: on the Mac, Share this Mac should show Sharing active, and your TYO ID must appear under Shared with…. See Share this PC.

Which VNC client should I use?

Any standard VNC client works once the setting above is on — Remmina or TigerVNC on Linux, TightVNC or RealVNC Viewer on Windows. Reach launches your default VNC client automatically when you click the machine.

Is the VNC password sent in the clear?

The password exchange is VNC's own challenge-response, and the whole session travels inside Reach's encrypted tunnel to the Mac — nothing goes over the open internet unencrypted.

Still stuck?

Get in touch with the client you're using and the exact message it shows.