How to resolve X11 authentication error

Environment

Linux/macOS/Windows with X11 server

OpenSSH client with X11 forwarding enabled

X11 applications

Issue

When running X11 applications after enabling X11 forwarding, encountered authentication error
username@hpcname:~$ firefox
X11 connection rejected because of wrong authentication
Error: cannot open display: localhost:10.0

Resolution

Set the XAUTHORITY environment variable to point to the correct xauth file
```
export XAUTHORITY="$HOME/.Xauthority"
```
Launch the application again
```
username@hpcname:~$ firefox
```

Root Cause

X11 forwarding requires proper authentication between the client and server.

While some applications defaults to look for xauth file at ~/.Xauthority, some X11 applications may require setting the XAUTHORITY environment variable explicitly.