GEMFILE(5) File Formats Manual GEMFILE(5)
NAME
Gemfile - A format for describing gem dependencies for Ruby programs
SYNOPSIS
A Gemfile describes the gem dependencies required to execute associated
Ruby code.
Place the Gemfile in the root of the directory containing the associated
code. For instance, in a Rails application, place the Gemfile in the
same directory as the Rakefile.
SYNTAX
A Gemfile is evaluated as Ruby code, in a context which makes available
a number of methods used to describe the gem requirements.
GLOBAL SOURCE
At the top of the Gemfile, add a single line for the RubyGems source
that contains the gems listed in the Gemfile.
source "https://rubygems.org"
You can add only one global source. In Bundler 1.13, adding multiple
global sources was deprecated. The source MUST be a valid RubyGems
repository.
To use more than one source of RubyGems, you should use source block.
A source is checked for gems following the heuristics described in
SOURCE PRIORITY.
Note about a behavior of the feature deprecated in Bundler 1.13: If a
gem is found in more than one global source, Bundler will print a warn-
ing after installing the gem indicating which source was used, and list-
ing the other sources where the gem is available. A specific source can
be selected for gems that need to use a non-standard repository, sup-
pressing this warning, by using the :source option or source block.
CREDENTIALS
Some gem sources require a username and password. Use bundle config(1)
bundle-config.1.html to set the username and password for any of the
sources that need it. The command must be run once on each computer that
will install the Gemfile, but this keeps the credentials from being
stored in plain text in version control.
bundle config gems.example.com user:password
For some sources, like a company Gemfury account, it may be easier to
include the credentials in the Gemfile as part of the source URL.
source "https://user:password@gems.example.com"
Credentials in the source URL will take precedence over credentials set
using config.
RUBY
If your application requires a specific Ruby version or engine, specify
your requirements using the ruby method, with the following arguments.
All parameters are OPTIONAL unless otherwise specified.
VERSION (required)
The version of Ruby that your application requires. If your application
requires an alternate Ruby engine, such as JRuby, TruffleRuby, etc.,
this should be the Ruby version that the engine is compatible with.
ruby "3.1.2"
If you wish to derive your Ruby version from a version file (ie
.ruby-version), you can use the file option instead.
ruby file: ".ruby-version"
The version file should conform to any of the following formats:
• 3.1.2 (.ruby-version)
• ruby 3.1.2 (.tool-versions, read: https://asdf-vm.com/manage/config-
uration.html#tool-versions)
ENGINE
Each application may specify a Ruby engine. If an engine is specified,
an engine version must also be specified.
What exactly is an Engine?
• A Ruby engine is an implementation of the Ruby language.
• For background: the reference or original implementation of the Ruby
programming language is called Matz's Ruby Interpreter
https://en.wikipedia.org/wiki/Ruby_MRI, or MRI for short. This is
named after Ruby creator Yukihiro Matsumoto, also known as Matz. MRI
is also known as CRuby, because it is written in C. MRI is the most
widely used Ruby engine.
• Other implementations https://www.ruby-lang.org/en/about/ of Ruby
exist. Some of the more well-known implementations include JRuby
https://www.jruby.org/ and TruffleRuby
https://www.graalvm.org/ruby/. Rubinius is an alternative implemen-
tation of Ruby written in Ruby. JRuby is an implementation of Ruby
on the JVM, short for Java Virtual Machine. TruffleRuby is a Ruby
implementation on the GraalVM, a language toolkit built on the JVM.
ENGINE VERSION
Each application may specify a Ruby engine version. If an engine version
is specified, an engine must also be specified. If the engine is "ruby"
the engine version specified must match the Ruby version.
ruby "2.6.8", engine: "jruby", engine_version: "9.3.8.0"
PATCHLEVEL
Each application may specify a Ruby patchlevel. Specifying the patch-
level has been meaningless since Ruby 2.1.0 was released as the patch-
level is now uniquely determined by a combination of major, minor, and
teeny version numbers.
This option was implemented in Bundler 1.4.0 for Ruby 2.0 or earlier.
ruby "3.1.2", patchlevel: "20"
GEMS
Specify gem requirements using the gem method, with the following argu-
ments. All parameters are OPTIONAL unless otherwise specified.
NAME (required)
For each gem requirement, list a single gem line.
gem "nokogiri"
VERSION
Each gem MAY have one or more version specifiers.
gem "nokogiri", ">= 1.4.2"
gem "RedCloth", ">= 4.1.0", "< 4.2.0"
REQUIRE AS
Each gem MAY specify files that should be used when autorequiring via
Bundler.require. You may pass an array with multiple files or true if
the file you want required has the same name as gem or false to prevent
any file from being autorequired.
gem "redis", require: ["redis/connection/hiredis", "redis"]
gem "webmock", require: false
gem "byebug", require: true
The argument defaults to the name of the gem. For example, these are
identical:
gem "nokogiri"
gem "nokogiri", require: "nokogiri"
gem "nokogiri", require: true
GROUPS
Each gem MAY specify membership in one or more groups. Any gem that does
not specify membership in any group is placed in the default group.
gem "rspec", group: :test
gem "wirble", groups: [:development, :test]
The Bundler runtime allows its two main methods, Bundler.setup and
Bundler.require, to limit their impact to particular groups.
# setup adds gems to Ruby's load path
Bundler.setup # defaults to all groups
require "bundler/setup" # same as Bundler.setup
Bundler.setup(:default) # only set up the _default_ group
Bundler.setup(:test) # only set up the _test_ group (but `not` _default_)
Bundler.setup(:default, :test) # set up the _default_ and _test_ groups, but no others
# require requires all of the gems in the specified groups
Bundler.require # defaults to the _default_ group
Bundler.require(:default) # identical
Bundler.require(:default, :test) # requires the _default_ and _test_ groups
Bundler.require(:test) # requires the _test_ group
The Bundler CLI allows you to specify a list of groups whose gems bundle
install should not install with the without configuration.
To specify multiple groups to ignore, specify a list of groups separated
by spaces.
bundle config set --local without test
bundle config set --local without development test
Also, calling Bundler.setup with no parameters, or calling require
"bundler/setup" will setup all groups except for the ones you excluded
via --without (since they are not available).
Note that on bundle install, bundler downloads and evaluates all gems,
in order to create a single canonical list of all of the required gems
and their dependencies. This means that you cannot list different ver-
sions of the same gems in different groups. For more details, see Under-
standing Bundler https://bundler.io/rationale.html.
PLATFORMS
If a gem should only be used in a particular platform or set of plat-
forms, you can specify them. Platforms are essentially identical to
groups, except that you do not need to use the --without install-time
flag to exclude groups of gems for other platforms.
There are a number of Gemfile platforms:
ruby C Ruby (MRI), Rubinius, or TruffleRuby, but not Windows
mri C Ruby (MRI) only, but not Windows
windows
Windows C Ruby (MRI), including RubyInstaller 32-bit and 64-bit
versions
mswin Windows C Ruby (MRI), including RubyInstaller 32-bit versions
mswin64
Windows C Ruby (MRI), including RubyInstaller 64-bit versions
rbx Rubinius
jruby JRuby
truffleruby
TruffleRuby
On platforms ruby, mri, mswin, mswin64, and windows, you may addition-
ally specify a version by appending the major and minor version numbers
without a delimiter. For example, to specify that a gem should only be
used on platform ruby version 3.1, use:
ruby_31
As with groups (above), you may specify one or more platforms:
gem "weakling", platforms: :jruby
gem "ruby-debug", platforms: :mri_31
gem "nokogiri", platforms: [:windows_31, :jruby]
All operations involving groups (bundle install bundle-install.1.html,
Bundler.setup, Bundler.require) behave exactly the same as if any groups
not matching the current platform were explicitly excluded.
The following platform values are deprecated and should be replaced with
windows:
• mswin, mswin64, mingw32, x64_mingw
Note that, while unfortunately using the same terminology, the values of
this option are different from the values that bundle lock --add-plat-
form can take. The values of this option are more closer to "Ruby Imple-
mentation" while the values that bundle lock --add-platform understands
are more related to OS and architecture of the different systems where
your lockfile will be used.
FORCE_RUBY_PLATFORM
If you always want the pure ruby variant of a gem to be chosen over
platform specific variants, you can use the force_ruby_platform option:
gem "ffi", force_ruby_platform: true
This can be handy (assuming the pure ruby variant works fine) when:
• You're having issues with the platform specific variant.
• The platform specific variant does not yet support a newer ruby (and
thus has a required_ruby_version upper bound), but you still want
your Gemfile{.lock} files to resolve under that ruby.
SOURCE
You can select an alternate RubyGems repository for a gem using the
':source' option.
gem "some_internal_gem", source: "https://gems.example.com"
This forces the gem to be loaded from this source and ignores the global
source declared at the top level of the file. If the gem does not exist
in this source, it will not be installed.
Bundler will search for child dependencies of this gem by first looking
in the source selected for the parent, but if they are not found there,
it will fall back on the global source.
Note about a behavior of the feature deprecated in Bundler 1.13: Select-
ing a specific source repository this way also suppresses the ambiguous
gem warning described above in GLOBAL SOURCE.
Using the :source option for an individual gem will also make that
source available as a possible global source for any other gems which do
not specify explicit sources. Thus, when adding gems with explicit
sources, it is recommended that you also ensure all other gems in the
Gemfile are using explicit sources.
GIT
If necessary, you can specify that a gem is located at a particular git
repository using the :git parameter. The repository can be accessed via
several protocols:
HTTP(S)
gem "rails", git: "https://github.com/rails/rails.git"
SSH gem "rails", git: "git@github.com:rails/rails.git"
git gem "rails", git: "git://github.com/rails/rails.git"
If using SSH, the user that you use to run bundle install MUST have the
appropriate keys available in their $HOME/.ssh.
NOTE: http:// and git:// URLs should be avoided if at all possible.
These protocols are unauthenticated, so a man-in-the-middle attacker can
deliver malicious code and compromise your system. HTTPS and SSH are
strongly preferred.
The group, platforms, and require options are available and behave ex-
actly the same as they would for a normal gem.
A git repository SHOULD have at least one file, at the root of the di-
rectory containing the gem, with the extension .gemspec. This file MUST
contain a valid gem specification, as expected by the gem build command.
If a git repository does not have a .gemspec, bundler will attempt to
create one, but it will not contain any dependencies, executables, or C
extension compilation instructions. As a result, it may fail to properly
integrate into your application.
If a git repository does have a .gemspec for the gem you attached it to,
a version specifier, if provided, means that the git repository is only
valid if the .gemspec specifies a version matching the version speci-
fier. If not, bundler will print a warning.
gem "rails", "2.3.8", git: "https://github.com/rails/rails.git"
# bundle install will fail, because the .gemspec in the rails
# repository's master branch specifies version 3.0.0
If a git repository does not have a .gemspec for the gem you attached it
to, a version specifier MUST be provided. Bundler will use this version
in the simple .gemspec it creates.
Git repositories support a number of additional options.
branch, tag, and ref
You MUST only specify at most one of these options. The default
is branch: "master". For example:
gem "rails", git: "https://github.com/rails/rails.git", branch:
"5-0-stable"
gem "rails", git: "https://github.com/rails/rails.git", tag:
"v5.0.0"
gem "rails", git: "https://github.com/rails/rails.git", ref:
"4aded"
submodules
For reference, a git submodule
https://git-scm.com/book/en/v2/Git-Tools-Submodules lets you have
another git repository within a subfolder of your repository.
Specify submodules: true to cause bundler to expand any submod-
ules included in the git repository
If a git repository contains multiple .gemspecs, each .gemspec repre-
sents a gem located at the same place in the file system as the .gem-
spec.
|~rails [git root]
| |-rails.gemspec [rails gem located here]
|~actionpack
| |-actionpack.gemspec [actionpack gem located here]
|~activesupport
| |-activesupport.gemspec [activesupport gem located here]
|...
To install a gem located in a git repository, bundler changes to the di-
rectory containing the gemspec, runs gem build name.gemspec and then in-
stalls the resulting gem. The gem build command, which comes standard
with Rubygems, evaluates the .gemspec in the context of the directory in
which it is located.
GIT SOURCE
A custom git source can be defined via the git_source method. Provide
the source's name as an argument, and a block which receives a single
argument and interpolates it into a string to return the full repo ad-
dress:
git_source(:stash){ |repo_name| "https://stash.corp.acme.pl/#{repo_name}.git" }
gem 'rails', stash: 'forks/rails'
In addition, if you wish to choose a specific branch:
gem "rails", stash: "forks/rails", branch: "branch_name"
GITHUB
NOTE: This shorthand should be avoided until Bundler 2.0, since it cur-
rently expands to an insecure git:// URL. This allows a man-in-the-mid-
dle attacker to compromise your system.
If the git repository you want to use is hosted on GitHub and is public,
you can use the :github shorthand to specify the github username and
repository name (without the trailing ".git"), separated by a slash. If
both the username and repository name are the same, you can omit one.
gem "rails", github: "rails/rails"
gem "rails", github: "rails"
Are both equivalent to
gem "rails", git: "https://github.com/rails/rails.git"
Since the github method is a specialization of git_source, it accepts a
:branch named argument.
You can also directly pass a pull request URL:
gem "rails", github: "https://github.com/rails/rails/pull/43753"
Which is equivalent to:
gem "rails", github: "rails/rails", branch: "refs/pull/43753/head"
GIST
If the git repository you want to use is hosted as a GitHub Gist and is
public, you can use the :gist shorthand to specify the gist identifier
(without the trailing ".git").
gem "the_hatch", gist: "4815162342"
Is equivalent to:
gem "the_hatch", git: "https://gist.github.com/4815162342.git"
Since the gist method is a specialization of git_source, it accepts a
:branch named argument.
BITBUCKET
If the git repository you want to use is hosted on Bitbucket and is pub-
lic, you can use the :bitbucket shorthand to specify the bitbucket user-
name and repository name (without the trailing ".git"), separated by a
slash. If both the username and repository name are the same, you can
omit one.
gem "rails", bitbucket: "rails/rails"
gem "rails", bitbucket: "rails"
Are both equivalent to
gem "rails", git: "https://rails@bitbucket.org/rails/rails.git"
Since the bitbucket method is a specialization of git_source, it accepts
a :branch named argument.
PATH
You can specify that a gem is located in a particular location on the
file system. Relative paths are resolved relative to the directory con-
taining the Gemfile.
Similar to the semantics of the :git option, the :path option requires
that the directory in question either contains a .gemspec for the gem,
or that you specify an explicit version that bundler should use.
Unlike :git, bundler does not compile C extensions for gems specified as
paths.
gem "rails", path: "vendor/rails"
If you would like to use multiple local gems directly from the filesys-
tem, you can set a global path option to the path containing the gem's
files. This will automatically load gemspec files from subdirectories.
path 'components' do
gem 'admin_ui'
gem 'public_ui'
end
BLOCK FORM OF SOURCE, GIT, PATH, GROUP and PLATFORMS
The :source, :git, :path, :group, and :platforms options may be applied
to a group of gems by using block form.
source "https://gems.example.com" do
gem "some_internal_gem"
gem "another_internal_gem"
end
git "https://github.com/rails/rails.git" do
gem "activesupport"
gem "actionpack"
end
platforms :ruby do
gem "ruby-debug"
gem "sqlite3"
end
group :development, optional: true do
gem "wirble"
gem "faker"
end
In the case of the group block form the :optional option can be given to
prevent a group from being installed unless listed in the --with option
given to the bundle install command.
In the case of the git block form, the :ref, :branch, :tag, and :submod-
ules options may be passed to the git method, and all gems in the block
will inherit those options.
The presence of a source block in a Gemfile also makes that source
available as a possible global source for any other gems which do not
specify explicit sources. Thus, when defining source blocks, it is rec-
ommended that you also ensure all other gems in the Gemfile are using
explicit sources, either via source blocks or :source directives on in-
dividual gems.
INSTALL_IF
The install_if method allows gems to be installed based on a proc or
lambda. This is especially useful for optional gems that can only be
used if certain software is installed or some other conditions are met.
install_if -> { RUBY_PLATFORM =~ /darwin/ } do
gem "pasteboard"
end
GEMSPEC
The .gemspec https://guides.rubygems.org/specification-reference/ file
is where you provide metadata about your gem to Rubygems. Some required
Gemspec attributes include the name, description, and homepage of your
gem. This is also where you specify the dependencies your gem needs to
run.
If you wish to use Bundler to help install dependencies for a gem while
it is being developed, use the gemspec method to pull in the dependen-
cies listed in the .gemspec file.
The gemspec method adds any runtime dependencies as gem requirements in
the default group. It also adds development dependencies as gem require-
ments in the development group. Finally, it adds a gem requirement on
your project (path: '.'). In conjunction with Bundler.setup, this allows
you to require project files in your test code as you would if the
project were installed as a gem; you need not manipulate the load path
manually or require project files via relative paths.
The gemspec method supports optional :path, :glob, :name, and :develop-
ment_group options, which control where bundler looks for the .gemspec,
the glob it uses to look for the gemspec (defaults to: {,*,*/*}.gem-
spec), what named .gemspec it uses (if more than one is present), and
which group development dependencies are included in.
When a gemspec dependency encounters version conflicts during resolu-
tion, the local version under development will always be selected --
even if there are remote versions that better match other requirements
for the gemspec gem.
SOURCE PRIORITY
When attempting to locate a gem to satisfy a gem requirement, bundler
uses the following priority order:
1. The source explicitly attached to the gem (using :source, :path, or
:git)
2. For implicit gems (dependencies of explicit gems), any source, git,
or path repository declared on the parent. This results in bundler
prioritizing the ActiveSupport gem from the Rails git repository
over ones from rubygems.org
3. If neither of the above conditions are met, the global source will
be used. If multiple global sources are specified, they will be pri-
oritized from last to first, but this is deprecated since Bundler
1.13, so Bundler prints a warning and will abort with an error in
the future.
March 2025 GEMFILE(5)
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