Must set build.dir Must set build.generated.dir Must set dist.dir Must set build.classes.excludes Must set dist.jar The libs.CopyLibs.classpath property is not set up. This property must point to org-netbeans-modules-java-j2seproject-copylibstask.jar file which is part of NetBeans IDE installation and is usually located at <netbeans_installation>/java<version>/ant/extra folder. Either open the project in the IDE and make sure CopyLibs library exists or setup the property manually. For example like this: ant -Dlibs.CopyLibs.classpath=a/path/to/org-netbeans-modules-java-j2seproject-copylibstask.jar Browser not found, cannot launch the deployed application. Try to set the BROWSER environment variable. Launching ${browse.url}