rubyfmt

April 4, 2026 · View on GitHub

A fast, opinionated Ruby formatter written in Rust.

Try it online → rubyfmt.run

Pronunciation: (en) "Ruby Format", (jp) ルビーフォーマット

Quick Start

# Install
brew install rubyfmt

# Format a file in place
rubyfmt -i myfile.rb

# Format and print to stdout
rubyfmt myfile.rb

Installation

Homebrew

brew install rubyfmt

Build from Source

Make sure you have Cargo installed
Run cargo build --release
Copy target/release/rubyfmt-main to somewhere on your path as rubyfmt

Usage

Command Line

Command	Description
`rubyfmt file.rb`	Output formatted code to stdout
`rubyfmt -i file.rb`	Format file in place
`rubyfmt -c file.rb`	Show diff of changes
`cat file.rb \| rubyfmt`	Read from stdin

You can also pass directories to format multiple files at once.

For the full command line interface, see rubyfmt --help.

Header Comments

Control formatting on a per-file basis with header comments:

rubyfmt --header-opt-in - Only format files with # rubyfmt: true at the top
rubyfmt --header-opt-out - Skip files with # rubyfmt: false at the top

Ignoring Files

Create a .rubyfmtignore file in your project root to exclude files from formatting. It uses the same syntax as .gitignore.

By default, rubyfmt also respects your .gitignore. Use --include-gitignored to format those files anyway.

Editor Integration

Visual Studio Code

The popular ruby-lsp extension has a rubyfmt add-on. Install the extension:

# Add to project
bundle add ruby-lsp-rubyfmt-formatter --group development

# Install globally
gem install ruby-lsp-rubyfmt-formatter

And then add the following to your .vscode/settings.json:

{
  "[ruby]": {
    "editor.defaultFormatter": "Shopify.ruby-lsp",
    "editor.formatOnSave": true
  },
  "rubyLsp.formatter": "rubyfmt"
}

Rubyfmt is also supported by the (now-deprecated) VSCode Ruby extension. Add the following to your settings.json:

{
  "ruby.useLanguageServer": true,
  "ruby.format": "rubyfmt",
  "[ruby]": {
    "editor.formatOnSave": true
  }
}

This is additionally supported by the Formatto for VS Code extension. Use it as your project's formatter by adding this entry to your .vscode/settings.json after installing the extension:

{
  "[ruby]": {
    "editor.defaultFormatter": "damolinx.formatto"
  },
}

Check its README for additional configuration options.

Neovim + null-ls

The null-ls plugin supports rubyfmt out of the box:

null_ls.setup({
  sources = {
    null_ls.builtins.formatting.rubyfmt,
  },
})

See the null-ls documentation for more details.

Vim

Run cargo build --release
Add source /path/to/rubyfmt.vim to your ~/.vimrc
Add let g:rubyfmt_path = /path/to/target/release/rubyfmt-main beneath the source line

RubyMine (and JetBrains IDEs)

Install the File Watchers plugin
Go to File | Settings | Tools | File Watchers
Import watchers.xml from editor_plugins/rubymine/
Optionally set Level to Global for all projects

See the File Watchers documentation for more details.

Sublime Text

Install the rubyfmt plugin via Package Control.

Files format on save or with Cmd + ; (macOS) / Alt + ; (other). Settings:

{
  "ruby_executable": "ruby",
  "rubyfmt_executable": "rubyfmt",
  "format_on_save": true
}