fnm vs nvm: Node Version Managers for CI
fnm is a fast, Rust-based Node version manager; nvm is the original shell-based one that nearly everyone has used.
Both install and switch Node.js versions and read a project version file. fnm is a compiled binary that starts quickly and reads .node-version or .nvmrc; nvm is a Bash script that is universal but slow to source in a shell.
| fnm | nvm | |
|---|---|---|
| Implementation | Rust binary | Bash script |
| Shell startup overhead | Low | Noticeable (sources script) |
| Version file | .node-version / .nvmrc | .nvmrc |
| Auto-switch on cd | Yes (with shell hook) | Via extra config |
| Ubiquity | Growing | Very widely documented |
Where fnm wins
As a single binary, fnm installs cleanly in CI and adds little shell startup overhead, which matters when many steps spawn shells. It reads both .node-version and .nvmrc, so it slots into existing repos. Auto-switching on directory change is smooth with the shell hook.
Where nvm wins
nvm is the most documented option and is what most guides and onboarding assume. For local developer machines where startup speed is not critical, its ubiquity and familiarity are real advantages. Many teams already have nvm muscle memory.
In CI
On GitHub Actions, the simplest path is usually actions/setup-node reading .nvmrc, no version manager needed. Reach for fnm or nvm when you need on-the-fly switching mid-job; fnm is the leaner choice for pipeline speed.
The verdict
Pick fnm for speed and a clean single-binary install, especially in CI or for fast shells; pick nvm for maximum familiarity on local machines. For most pipelines, setup-node with a version file avoids needing either.