It seems that firefox 68.x, as distributed with CentOS6 updates, no longer allows opening jnlp files with javaws The "Choose Helper Application" window popping up after selecting "Open with/Other" has a predefined list of applications that cannot be customised. I'm sure it must be a configuration issue as this works fine with the same browser on other distributions, but what to look for? # alternatives --display javaws javaws - status is auto. link currently points to /usr/java/latest/jre/bin/javaws /usr/java/latest/jre/bin/javaws - priority 200000 Current `best' version is /usr/java/latest/jre/bin/javaws. # ll -L /etc/alternatives/javaws -rwxr-xr-x 1 root root 140296 Dec 15 2018 /etc/alternatives/javaws #