Signal-exit is a Node.js library that provides a reliable way to execute cleanup code or trigger events when a process exits, regardless of the exit method—whether it's reaching the end of execution, calling `process.exit()`, receiving a signal, or being killed externally. It's designed for developers who need to ensure graceful shutdowns or cleanup in Node.js applications, particularly when handling signals or unexpected terminations. The library also includes a browser fallback, though its functionality is limited in that environment.