Fingerprintable is an easy way to fingerprint any object in Ruby. It handles cycles and allows you to override what attributes you want to include in the fingerprint.

By default, Fingerprintable will use all instance variables of an object.


Add this line to your application's Gemfile:

gem 'fingerprintable'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fingerprintable


You can call Fingerprintable::Fingerprinter directly, or you can add Fingerprintable::Mixin to any class like so:

module Fingerprintable
  class MixinTestObject
    include Fingerprintable::Mixin

    attr_accessor :foo, :bar

    fingerprint :baz,
                ignore: :bar

    fingerprint :asdf

    def initialize(foo = nil) = foo

This results in a fingerprint being generated for these attributes: [:@foo, :asdf, :baz]

To get a fingerprint of any instance, just call .fingerprint.


After checking out the repo, run bin/setup to install dependencies. Then, run bundle exec rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


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

Code of Conduct

Everyone interacting in the Fingerprintable project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.