Understanding performance of Java code is hard, because the actual executed program is created on the fly by the JIT compiler. JITWatch is a log analyser for Java HotSpot JIT compiler. It consumes JIT log files and visualizes the compilation activity. This article describes how to get started with JITWatch in a project and what data is immediately useful to look at. JITWatch is an excellent tool that gives a visual feedback about what is happening within your application for anyone who is interested in JVM performance.