Hello, I have posted a thread similar to this, but I'm still not clear as to how X11 works or -X forwarding for that matter. I have some issues/questions about -X forwarding from one mac machine to another mac machine. Is it possible to use either xterm or the terminal to open any gui (such as Safari say...), or do I need an X11 specific version of the program? Here are my relevant settings On my local mac machine: DISPLAY is set to /tmp/launch-RuXg5G/org.x:0 and X11forwarding is yes in my /etc/sshd_config file On my remote mac machine: DISPLAY is localhost:12.0 and X11forwarding is yes in my /etc/sshd_config file I am able to use xedit and xterm on my local machine that is forwarded from the remote machine. However unable to get Safari or Preview to forward. So if I'm ssh'd into my remote machine and I enter "/Applications/Safari.app/Contents/MacOS/Safari &" I get the error Safari <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL. Likewise if I run "/Applications/Preview.app/Contents/MacOS/Preview some.pdf" I get the error Preview <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL. 2011-03-20 15:19:38.153 Preview[17986:903] Error (1002) creating CGSWindow This is highly aggravating b/c I can log (with ssh -X from my terminal) into a linux cluster (which i do not manage) and I simply type "firefox &" and loe and behold I get firefox forwarded to my local machine. I feel that I've searched extensively on how to fix this, and to say the least there isn't much out there or I don't know where to look. I had previously asked about using "open some.pdf" and I had gotten response to use an X11 based .pdf viewer or to do Remote Desktop/VNC/Screen Sharing. I'm not a big fan trying to use a Remote Desktop b/c I'd imagine the overhead is probably much higher than X forwarding, and my home internet connection is bad enough. Plus, why can't/why shouldn't Mac OSX have the "just work simplicity of linux machines." Anyhow, thanks for any help in advance!