Sure. You need to edit the greenfoot.defs file (normally in greenfoot_root/lib/greenfoot.defs, where greenfoot_root is where you installed Greenfoot; if on a Mac, ctrl + click the application and choose "show package contents", then navigate through Content / Resources / Java). Find the proxy settings in that file: #proxy.host= #proxy.port=80 You need to fill in the correct values, and remove the '#'. Note that the proxy.host is just the host, it is not a URL! So for example: proxy.host=proxy.myschool.edu proxy.port=8080 (Those are just example values - you must use the correct values for your proxy).