asdf vs fnm

asdf is a free, open-source version manager for Linux and macOS. It gives project teams one command interface and a shared `.tool-versions` file for selecting exact versions of multiple tools and runtimes. Plugins support tools such as Node.js, Ruby, and Elixir, while the plugin API allows additional tools. When a command runs, asdf searches for configuration from the current directory upward toward the home directory, then uses shims to launch the selected executable. Existing `.ruby-version`, `.nvmrc`, and `.node-version` files can be supported per plugin. Listed shell support includes Bash, ZSH, Fish, and Elvish, with completions. A GitHub Action uses `.tool-versions` in CI/CD workflows. Installation options include Homebrew, Zypper, Pacman, precompiled binaries, Go, and source builds. asdf manages tool versions rather than system packages or upstream dependencies. If no version is set, execution errors unless the tool is configured as `system`.

fnm is a free Node.js version manager built in Rust for developers working from a command line or shell. It runs on macOS, Windows, and Linux, and is distributed as a single file through installation scripts, package managers, Cargo, or release binaries. It reads `.node-version` and `.nvmrc` files, so projects can specify a Node.js version. Shell setup can also enable automatic version switching when changing directories. The project provides setup instructions for Bash, Zsh, Fish, PowerShell, Windows Command Prompt, and Cmder. Its binary includes completions for Bash, Zsh, Fish, and PowerShell. On macOS and Linux, the installation script requires `curl` and `unzip`. The repository identifies the license as GPL-3.0 and invites pull requests, with issues available for project interaction. No paid plans are listed. The project page reports no published security advisories, while also noting that it has not set up a SECURITY.md file.