frum

frum is a free, MIT-licensed tool for managing Ruby versions, best suited to developers who want project-level pins alongside a machine-wide default. Its focused scope and shell support are appealing; teams seeking a broader environment manager should look elsewhere.

Overview

frum handles the main version-management tasks: installing and removing Ruby versions, listing available or installed versions, and choosing a local or global version. Project pins use .ruby-version, with automatic switching to apply the project’s choice as you move between repositories. This keeps project requirements separate from your global default without adding a multi-language environment layer.

The implementation is pure Rust and does not use ruby-build. The project reports that evaluating frum init runs about six times faster than evaluating rbenv init in its benchmark. That comparison is relevant to shell initialization, not a claim that Ruby builds or applications run six times faster.

Key features

Ruby version control

Local and global selection, project files, and automatic switching make frum a practical fit for developers working across repositories that require different Ruby versions. Its commands also cover installation, uninstallation, and version listings, so the core workflow stays within one tool.

Configurable builds and shell setup

Ruby installation accepts options such as an OpenSSL directory and jemalloc allocator selection, which gives developers control over build configuration. Bash, Zsh, and Fish setup instructions and auto-completion are useful for common shell workflows. The README documents installation through Homebrew or Linuxbrew, Arch Linux packages, Cargo, and release binaries.

Pricing

frum costs free. The free plan is the tool itself, with MIT licensing; there is no paid tier or trial to weigh against it. That makes it easy to adopt for individual Ruby development, though its single-language scope is the trade-off rather than a cheaper plan withholding broader capabilities.

Platforms

frum supports macOS and Linux, with installation routes including package managers, Cargo, and release binaries. Windows appears in the project’s goals, but is not among the operating systems its README identifies as supported; Windows users should not assume the same level of support as on macOS or Linux.

Who it's for

Choose frum if Ruby is your target language and you want project-specific versions, a global default, shell integration, and configurable builds without paying for a version manager. It is less suited to developers looking for one system to coordinate multiple languages or a broader development environment.

Pros and cons

• Pros: Free and MIT-licensed, with local and global Ruby selection, .ruby-version support, and automatic switching for project workflows.
• Pros: Bash, Zsh, and Fish setup plus completion cover common shell use, and build options include OpenSSL directory and jemalloc selection.
• Cons: Its scope is limited to Ruby, so it is not a replacement for a multi-language environment manager.
• Cons: Windows is a project goal rather than a platform the README identifies as supported.

Alternatives

Development Environment Managers is a useful starting point if you want to compare tools beyond Ruby version management.

• GHCup is the free option to consider for Haskell toolchain installation and management rather than Ruby version control.
• ActiveState Platform may suit teams that need an organization-focused platform: its free plan is limited to public projects, and paid organization pricing is custom.
• devenv is a free, MIT-licensed alternative for broader environment management if you can work with its Nix requirement.
• Flox is worth considering if you want a broader environment tool and its Personal plan’s public and private FloxHub environment allowances fit your needs.
• FVM is a free alternative for Flutter SDK version management.
• Jabba is a free option for Java version management.
• vfox is another free version-management option if you want an Apache 2.0-licensed tool.
• DDEV is a free, Apache 2.0-licensed alternative to consider for a different development workflow.

Verdict

frum is a strong fit for Ruby developers who want local and global version control, automatic project switching, and shell integration at no cost. Its main reason to choose it is that focused Ruby workflow; look elsewhere if you need a multi-language environment manager or dependable Windows support.