rubocop-daemon makes RuboCop faster.


Install rubocop-daemon via

gem install rubocop-daemon

or if you install RuboCop using bundler, put this in your Gemfile:

gem 'rubocop-daemon', require: false


To start the server, just run:

rubocop-daemon start

Then you can execute RuboCop fast:

rubocop-daemon exec

And you can pass files:

rubocop-daemon exec foo.rb bar.rb

If you want to pass arguments to RuboCop, you should separate arguments by --:

rubocop-daemon exec -- --auto-correct


You can control the server like this:

rubocop-daemon <command>

Available commands:

  • start: start the server
  • stop: stop the server
  • status: print out whether the server is currently running
  • restart: restart the server
  • exec [file1, file2, ...] [-- [rubocop-options]]: invoke rubocop with the given rubocop-options

More speed

rubocop-daemon-wrapper is a bash script that talks to the rubocop-daemon server via netcat. This provides much lower latency than the rubocop-daemon Ruby script.

For now, you have to manually download and install the bash script:

(rubygems will wrap any executable files with a Ruby script, and you can't disable this behavior.)

curl -o /tmp/rubocop-daemon-wrapper
sudo mv /tmp/rubocop-daemon-wrapper /usr/local/bin/rubocop-daemon-wrapper
sudo chmod +x /usr/local/bin/rubocop-daemon-wrapper

You can then replace any calls to rubocop with rubocop-daemon-wrapper.

rubocop-daemon-wrapper foo.rb bar.rb

rubocop-daemon-wrapper will automatically start the daemon server if it is not already running. So the first call will be about the same as rubocop, but the second call will be much faster.

Use with Bundler

If you install rubocop-daemon with bundler, you should set RUBOCOP_DAEMON_USE_BUNDLER environment variable:


Now rubocop-daemon-wrapper will call the rubocop-daemon command with bundle exec.

Use with VS Code

Unfortunately, the vscode-ruby extension doesn't really allow you to customize the rubocop path or binary. (You can change the linter path, but not the formatter.)

In the meantime, you could just override the rubocop binary with a symlink to rubocop-daemon-wrapper:

# Find your rubocop path
$ which rubocop

# Override rubocop with a symlink to rubocop-daemon-wrapper
$ ln -fs /usr/local/bin/rubocop-daemon-wrapper $HOME/.rvm/gems/ruby-x.y.z/bin/rubocop

Or, if you use rbenv:

# which rubocop is rbenv running?
$ rbenv which rubocop

# Override rubocop with a symlink to rubocop-daemon-wrapper
$ ln -fs /usr/local/bin/rubocop-daemon-wrapper $HOME/.rbenv/versions/x.y.z/bin/rubocop

Now VS Code will use the rubocop-daemon-wrapper script, and formatOnSave should be much faster (~150ms instead of 3-5 seconds).

Use with Neovim/Vim8 and ALE

ALE setting example:

" Use `rubocop-daemon-wrapper` instead of `rubocop`
let g:ale_ruby_rubocop_executable = 'rubocop-daemon-wrapper'

Auto-correct on save setting example:

" optional: Set fixer(not only linter).
let g:ale_fixers = {
\   'ruby': ['rubocop'],

" optional: Auto-correct on save.
let g:ale_fix_on_save = 1


Bug reports and pull requests are welcome on GitHub at


The gem is available as open source under the terms of the MIT License.