Daemon vs Non-Daemon Threads: The JVM Rule Every Java Dev Must Know

The JVM shuts down only when all non-daemon threads have finished, completely ignoring any daemon threads still running at that point. Non-daemon status is the default for all threads, meaning threads spawned from the main thread inherit that status unless explicitly changed. Non-daemon threads are suited for critical work like network requests, where dropping an in-flight operation would be unacceptable. Daemon threads are better for optional background tasks such as analytics uploads, where terminating mid-execution causes no meaningful harm. Choosing the wrong type can either block JVM shutdown unexpectedly or silently kill important work in progress.