The -J option is non-standard and subject to change without notice. encoding Specify character encoding used by HTML files debug Start the applet viewer in the Java debugger I don't have any recollection of how one would run them. I have JDK 1.8 / Java 8 installed and it includes appletviewer.exe C:\Program Files\Java\jdk1.8.0_251\bin\appletviewer.exe I am trying to run some old java applets from the old book 'Algorithms and Data Structures In Java' by Robert LaFore.