open vnc://192.168.1.30Open Screen Sharing to another Mac by address.
When to use it
Use Screen Sharing to help someone or reach your own Mac across the house; use Remote Login for command-line access. Both are off by default, and they're the first things to check if you're worried about unwanted access.
Steps
Turn on Screen Sharing
On the Mac to share: System Settings › General › Sharing › Screen Sharing. Click ⓘ to allow only specific users.Connect from another Mac
Open the Screen Sharing app (Applications › Utilities), or Finder › Network, or open a vnc:// address.open vnc://192.168.1.30Turn on Remote Login for SSH
System Settings › General › Sharing › Remote Login. Limit it to your user.See who is connected
Active sessions show in the Screen Sharing menu bar icon on the shared Mac. For SSH,wholists logged-in users.who
Output explained
who lists sessions:
jane console Oct 24 09:12
jane ttys003 Oct 24 10:41 (192.168.1.23)
console is the person at the Mac; ttys entries with an address in brackets are SSH sessions from that address.
Ports: Screen Sharing (VNC) listens on 5900, Remote Login (SSH) on 22. Both are reachable from your local network when on; don't forward them from the internet, use a VPN or Tailscale for remote access instead.
Options and variations
| Flag | Meaning | Example |
|---|---|---|
| open vnc://HOST | Start Screen Sharing to a host | open vnc://mac-mini.local |
| ssh USER@HOST | Remote Login session | ssh jane@mac-mini.local |
| who / last | Current / recent logins | last | head |
Common errors
| Error | Cause | Fix |
|---|---|---|
| Connection failed to the other Mac | Screen Sharing off, or firewall blocks it | Turn it on; allow it in Firewall options. |
| Only a black screen | The shared Mac's display is asleep or locked at the login window | Wake it; log in through the window shown. |
Do it in the app
LightAtom's connections view shows incoming Screen Sharing and SSH sessions with the remote address, and its Ports view whether 5900 and 22 are listening.
Frequently asked questions
How do I share my Mac's screen with another Mac?
Turn on System Settings › General › Sharing › Screen Sharing, then connect from the other Mac with the Screen Sharing app or Finder › Network.
Is Screen Sharing safe on a Mac?
On a home network with strong passwords and access limited to specific users, yes. Don't expose port 5900 to the internet; use a VPN for remote access.
How do I know if someone is connected to my Mac?
A Screen Sharing icon appears in the menu bar during sessions. Run who to see SSH logins, and check Sharing settings for services you didn't turn on.