The NetBeans Profiler is based on a research project from Sun Laboratories. That research uncovered specific techniques that can be used to lower the overhead of profiling a Java application. One of those techniques is dynamic bytecode instrumentation, which is particularly useful for profiling large Java applications. Using dynamic bytecode instrumentation and additional algorithms, the NetBeans Profiler is able to obtain runtime information on applications that are too large or complex for other profilers. In addition, its dynamic capability means that profiling can be turned on and off for different parts of your application without requiring a restart. More info can be found here .