fnm is a version manager for Node.js. It helps developers keep several runtime versions available and switch between them, making it easier to work on projects that do not all use the same environment.
Match a project to its expected runtime
Use the Node.js version a repository needs when a dependency or build behaves differently from your current system installation.
Move between projects more easily
Keep versions for older products and newer prototypes without repeatedly replacing one global runtime. This supports a more predictable local development workflow.