Ever crashed a JVM? Then you typically get a HotSpot error file, or hs err for short. These files contain information about which crash occurred and what the JVM’s state was at the time of the crash. In this short blog post, we’ll be diving into the components of a typical hs err file and show case a few custom-built tools to work with them.

But before we start: A crashing JVM is normal when you develop the JVM, e.g., adding a new CPU-time profiler, but normally it should not happen (except maybe when your JVM runs out of memory), so the hs err files are not a common sight. Still, they are important to me and my colleagues at SapMachine, which is why I’m writing this blog post.

TL;DR: I wrote an online tool for redacting hs err files and also a syntax highlighter extension for VSCode, all as part of the jhserr project on GitHub.