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About Online Ruby Formatter

Paste your Ruby code, hit "Format" and instantly get clean, idiomatic output. Powered by Rufo-style formatting, this tool gives you consistent spacing and indentation for everything from tiny scripts to full Rails controllers — directly in your browser.

Why Use This Ruby Formatter

  • Rufo-style, opinionated formatting for consistent Ruby code
  • Normalizes indentation, blank lines and spacing around operators
  • Idempotent output – formatting the same file again produces the same result
  • Respects Ruby semantics – layout changes only, no behavior changes
  • Supports .rb, .rake and .gemspec files out of the box
  • Zero configuration: one-click Format, no complex settings required
  • Runs entirely in your browser UI – just paste or drop a file
  • Great companion to rubocop/standard as a layout-only formatter

🛠️ How to Use the Ruby Formatter for ruby-formatter

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1. Paste or Upload Your Ruby Code

📥 Paste Ruby code directly into the editor, or drag-and-drop a `.rb`, `.rake` or `.gemspec` file. The tool reads the content and prepares it for formatting.

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2. Click the Format Button

✨ Hit **Format** to send your code to the Rufo-style formatter. Indentation, line breaks and spacing are normalized in one pass while preserving the original logic.

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3. Review the Result

🔍 Compare the formatted output with your original Ruby code. You’ll see consistent indentation, cleaner blocks and more readable methods and conditionals.

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4. Copy or Download

📤 Once satisfied, copy the formatted code back to your editor or download it as a file. It’s ready for commits, pull requests or production deployments.

Technical Specifications

Formatting Engine & Style

The formatter follows Rufo-style, opinionated Ruby formatting rules to keep your codebase consistent and easy to scan in reviews.

AspectBehaviorNotes
IndentationTwo spaces per levelTabs are normalized to spaces to match idiomatic Ruby style.
Blocks & do/endAligned and indented consistentlyHelps keep nested blocks (each, map, if, case) readable.
WhitespaceCleans up excess spacesNormalizes spaces around operators, commas and symbols.
Blank linesStandardized between methods & classesImproves separation of concerns and visual grouping.
IdempotencySame input → same outputRe-running the formatter repeatedly is always safe.

Supported Input & Limits

Designed for real-world Ruby projects: gems, Rails apps, scripts and internal tooling.

ParameterLimit / BehaviorNotes
File extensions.rb, .rake, .gemspecTypical Ruby source files, Rake tasks and gem specifications.
MIME typestext/x-rubyHelps the editor select the Ruby language mode and syntax highlighting.
Max input size≈ 2 MB of Ruby sourceVery large sources or vendor bundles are better handled locally via CLI.
EncodingUTF-8 recommendedFor legacy encodings, convert to UTF-8 before formatting.

Safety & Execution

Formatting runs on a secured backend using a Ruby-aware formatter.

AspectBehaviorNotes
ExecutionSecure API call to formatterOnly the source code and basic options are sent to the formatting endpoint.
Timeout≈ 25 secondsVery long or pathological inputs are aborted to keep the UI responsive.
SemanticsLayout-only changesThe formatter is designed not to alter the behavior of valid Ruby code.

Command Line Alternatives for Ruby Formatting

Want the same style in your editor, CI or pre-commit hooks? Use Rufo or other Ruby formatters locally.

Linux / 🍎 macOS / 🪟 Windows

Install Rufo globally

gem install rufo

Adds the `rufo` executable to your Ruby environment.

Format a single Ruby file

rufo app/models/user.rb

Rewrites the file in place using Rufo rules.

Format an entire project

rufo .

Recursively formats all Ruby files in the current directory tree.

With pre-commit or CI

Add Rufo via pre-commit

repos:
- repo: https://github.com/ruby-formatter/rufo
  rev: v0.17.0
  hooks:
    - id: rufo

Runs Rufo automatically before each commit (YAML snippet for `.pre-commit-config.yaml`).

Use this online formatter for quick one-off fixes, and wire Rufo into your local tooling for full-project consistency.

Practical Use Cases for the Ruby Formatter

Ruby on Rails Applications

Clean up controllers, models and jobs before code review.

  • Normalize style across a team working on the same Rails app.
  • Auto-format files before opening pull requests.
  • Tidy scaffolding and generator output for long-term readability.
class UsersController < ApplicationController
  def create
      user = User.new(user_params)
   if user.save
redirect_to user_path(user)
else
 render :new
 end
  end
end

class UsersController < ApplicationController
  def create
    user = User.new(user_params)

    if user.save
      redirect_to user_path(user)
    else
      render :new
    end
  end
end

Gems, CLIs and Internal Tools

Keep gem source, Rake tasks and internal automation scripts tidy.

  • Apply consistent style before publishing a gem.
  • Clean noisy Rake files and deployment scripts.
  • Make internal CLI tools easier to maintain and extend.

Teaching & Learning Ruby

Show students how idiomatic Ruby looks without bikeshedding about style.

  • Auto-format student submissions before feedback so you can focus on logic.
  • Demonstrate the difference between "works" and "clean" Ruby.
  • Use the formatter in workshops to standardize examples quickly.
numbers=[1,2,3]
nums.each do |n| puts n*n end

numbers = [1, 2, 3]
numbers.each do |n|
  puts n * n
end

❓ Frequently Asked Questions

❓Will the Ruby formatter change how my code behaves?

The formatter is designed to only change layout: indentation, blank lines and whitespace. As long as your Ruby code is valid, the behavior should remain the same. You should still rely on your test suite to confirm everything is working as expected.

🧹How is this different from RuboCop or Standard?

RuboCop and Standard are primarily linters that can also auto-correct some issues, while this tool focuses purely on formatting. A formatter rewrites layout; a linter enforces a broader set of rules such as unused variables, naming conventions and complexity.

🔒Is it safe to paste production code into this tool?

Avoid pasting extremely sensitive or proprietary code into any online service. For highly sensitive projects, you should run Rufo or other formatters locally or in a self-hosted CI environment. For typical open source, demo or learning code, this online formatter is very convenient.

📂Which Ruby versions are supported?

The formatter targets modern Ruby syntax used in current Ruby and Rails projects. Very old Ruby syntax or edge-case metaprogramming may not format perfectly, in which case running the formatter directly in your Ruby environment is recommended.

⚡How fast is the formatting?

Most files format almost instantly. Only extremely large or heavily generated files might approach the built-in timeout. In those rare cases, format the file locally using the CLI.

Pro Tips

Best Practice

Use this formatter before opening a pull request so reviewers can focus on logic instead of whitespace.

Best Practice

Combine formatting with a linter like RuboCop or Standard to cover both layout and deeper quality issues.

Best Practice

Always run your test suite after large auto-formatting passes to ensure everything still behaves correctly.

Best Practice

For gems, apply formatting before bumping versions to avoid noisy diffs between releases.

Additional Resources

Ruby Style Guide
Documentation
Rufo – Ruby Formatter
Documentation
Ruby on Rails Guides
Documentation

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