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Lightweight Ruby debugger written in plain Ruby using the TracePoint API


~> 2.0
~> 5.11
>= 12.3.3
 Project Readme


Break is a lightweight debugger for Ruby. It's written in plain Ruby and doesn't have its own frontend. Once you put gem "break" in your Gemfile, it integrates seamlessly with IRB or Pry. You have navigational commands like next and step straight in your REPL session. You don't need to remember to start your debugger or change your development flow. Break embraces your flow, instead of forcing you to abide to yet another tool.


  • Control flow executing control.
  • No runtime cost. The tracing instructions kick in only when navigating.
  • Automatic integration with IRB and Pry.
  • Rails 6 constant auto loading support (not available in other Ruby debuggers).


Put gem "break" in your Gemfile. Then run bundle install and binding.irb (or binding.pry) to your heart's desire.


The following commands are available in both IRB and Pry.

Command Description
next Continue to next line.
step Step into method invocation.
up Go up the stack.
down Go down the stack.
whereami Show the code surrounding the current debugged line.
exit Disconnect the debugger and continue to run the program.


Add break in your application Gemfile and make sure to require "break" early in your program setup. In a Rails application, break will be required automatically and you don't need to worry about that.

gem "break"

Break automatically injects its commands into binding.irb and binding.pry (if available).

If you need to debug your program, type a next to go to the next line of program execution or step to step into a method, block, or class/module opening call. All of this, in the comfort of IRB or Pry. Simple!

Remote usage

Break can integrate with pry-remote for remote process debugging. You have to require break/remote for Break's integration to kick in.

You can declare break in your Gemfile with a custom require to get the remote integration loaded automatically by Bundler:

gem "break", require: "break/remote"

Why we need a debugger in Ruby?

We had our fair share of abandoned Ruby debuggers written in C. During Ruby 1.8 and Ruby 1.9 days, the interpreter itself changed often and didn't provide a stable API to aid the writing of development tools. This means that ruby-debug, a debugger written for Ruby 1.8 had to be rewritten for 1.9 (as a different gem: ruby-debug-base19) and then again for Ruby 2.0. At this point the development was halted as maintaining 3 different implementations is hard.

If we get better APIs in Ruby-land we won't run into the problems ruby-debug did. Even better, the debuggers can be thin layers on top of the heavy-lifting debugging instrumentation APIs that live in the interpreter themselves. This way the interpreter internals can change as much as they want but if they provide the same APIs, all of the debugging tools will still work. On top of that, our debuggers will work on JRuby, TruffleRuby or whatever alternative Ruby implementation is under active development at the time.

Break exists to implement a functional debugger in pure Ruby using the TracePoint API. It also wants to serve as a catalyst for other Ruby-land available APIs that are useful for implementing debugging tools.

Learn more from this Ruby Russia talk. ⚡️