Should Gemfile.lock Be Committed in Ruby? A Beginner-Friendly Guide

By the end of this page, you will understand what Gemfile.lock does, why Bundler creates it, and when it should or should not be committed. You will also learn the common rule used in Ruby projects: applications usually commit Gemfile.lock, while many libraries do not.

Gemfile.lock is Bundler's record of the exact gem versions that were resolved from your Gemfile.

Your Gemfile usually describes version rules, such as:

gem 'rails', '~> 7.1'

That means Bundler may choose a specific version that matches that rule, along with compatible versions of all dependent gems.

Gemfile.lock stores the final result of that resolution process. It answers questions like:

• Which exact version of rails was installed?
• Which versions of its dependencies were chosen?
• Which platforms were used?

This matters because dependency versions can change over time. Without a lock file, two developers might run bundle install on different days and get slightly different gem versions.

Why this matters

A lock file helps make environments consistent:

• your app works the same on your machine, CI, and production
• teammates install the same dependency versions
• bugs caused by unexpected dependency upgrades are reduced

The usual rule

In Ruby projects, the common convention is:

• Ruby applications: commit Gemfile.lock
• Ruby gems/libraries: often do not commit Gemfile.lock

Why?

• An application wants reproducible installs. It is the final thing being deployed.
• A library is meant to work with a range of dependency versions, so locking one exact set can be less useful and may even hide compatibility problems.

That means whether a pull request should include Gemfile.lock depends on the type of project and the existing project conventions.

Think of Gemfile as a shopping list with flexible rules and Gemfile.lock as the final receipt.

• Gemfile: "Buy a loaf of bread from this brand range."
• Gemfile.lock: "You bought exactly this bread, this milk, and these eggs."

If a whole team is cooking the same meal, using the same receipt helps everyone get identical ingredients.

But if you are publishing a recipe for other people to try in many kitchens, you may not want to force everyone to use the exact same brands from your receipt.

Bundler uses two main files:

Gemfile

This declares dependencies and version constraints.

source 'https://rubygems.org'

gem 'sinatra', '~> 3.0'
gem 'puma'

Gemfile.lock

This is generated by Bundler after running:

bundle install

A simplified lock file might look like this:

GEM
  remote: https://rubygems.org/
  specs:
    puma (6.4.2)
    rack (2.2.9)
    sinatra (3.1.0)
      rack (~> 2.2, >= 2.2.4)

PLATFORMS
  ruby

DEPENDENCIES
  puma
  sinatra (~> 3.0)

BUNDLED WITH
   2.5.10

What this means

• Gemfile says what your project needs.
• Gemfile.lock says exactly what Bundler chose.

Example decision

For an app:

# Usually do not ignore Gemfile.lock in apps

For a library, you might see:

Gemfile.lock

But always check the existing project style before changing it.

Practical guideline

• If the repository is a Rails app, Sinatra app, CLI app, or deployed service, commit Gemfile.lock.
• If the repository is a reusable gem, not committing it is often normal.

Consider this Gemfile:

source 'https://rubygems.org'

gem 'httparty', '~> 0.21'

Now run:

bundle install

What happens step by step

1. Bundler reads the Gemfile.
2. It sees that httparty is needed.
3. It looks for a version matching ~> 0.21.
4. It also finds all dependencies required by httparty.
5. It chooses exact versions that work together.
6. It installs those gems.
7. It writes the exact result into Gemfile.lock.

If another developer later runs:

bundle install

Bundler will prefer the versions already recorded in Gemfile.lock, which keeps the environment consistent.

Example trace

Suppose Bundler resolves:

• httparty -> 0.21.0
• one dependency -> exact compatible version

That exact combination is written into the lock file. Later, even if a newer compatible version exists, Bundler will keep using the locked version until the dependencies are intentionally updated.

Gemfile.lock is especially useful in real projects where consistency matters.

Web applications

A Rails app deployed to production should use the same gem versions in:

• local development
• test environments
• CI pipelines
• production servers

Team projects

When several developers work on the same app, the lock file prevents:

• "works on my machine" issues
• surprise upgrades after a fresh install
• different test results caused by different dependency versions

Deployment and CI

Build servers and deployment systems rely on predictable installs. A committed Gemfile.lock helps ensure the deployed app matches what was tested.

Bug fixing

If a bug appears only after a dependency changes, a lock file helps you identify exactly which version was in use.

Libraries and gems

For reusable gems, maintainers often test against multiple dependency versions instead of locking one exact install for all users. That is why many libraries do not commit Gemfile.lock.

In real Ruby codebases, developers usually follow project type and team conventions.

Common patterns

Application pattern

Applications usually commit both:

• Gemfile
• Gemfile.lock

This supports stable builds and safer deployments.

Library pattern

Libraries often commit:

• Gemfile

and may leave out:

• Gemfile.lock

This helps maintainers detect whether the library works across the allowed version ranges.

Team workflow

A common workflow looks like this:

1. Add or change a gem in Gemfile
2. Run bundle install
3. Review the changes in Gemfile.lock
4. Commit both files if the project commits lock files

Reviewing pull requests

When Gemfile.lock changes in a PR, developers usually check:

• whether the change was intentional
• whether only expected gems changed
• whether a platform or Bundler version change caused extra differences

Dependency update pattern

Teams often update gems deliberately using commands like:

bundle update

or updating a single gem:

bundle update rails

Then they commit the resulting Gemfile.lock changes so everyone uses the same updated versions.

1. Assuming Gemfile.lock should always be ignored

This is one of the most common beginner misunderstandings.

For applications, ignoring Gemfile.lock usually causes inconsistent installs.

2. Committing Gemfile.lock to a library without checking project convention

Some gems intentionally do not track it. If the repository has chosen that approach, adding it in a pull request may create noise or go against maintainer expectations.

3. Editing Gemfile.lock by hand

Usually, you should let Bundler generate and update it.

Broken approach:

# Manually changing versions in Gemfile.lock
    sinatra (3.2.0)

Better approach:

bundle install
# or
bundle update sinatra

4. Changing dependencies without reviewing the lock file

If you update Gemfile, Bundler may adjust several dependent gems too. Always review the lock file diff before committing.

5. Sending unrelated lock file changes in a pull request

If your PR is fixing a small bug but also updates many gems accidentally, maintainers may ask you to revert those changes.

6. Forgetting that project type matters

A Rails app and a reusable gem are not handled the same way.

Quick check

Ask:

• Is this a deployable app?
• Or is this a library meant to be used by other projects?

That usually tells you what to do.

Gemfile vs Gemfile.lock

Commit vs ignore

• Gemfile = dependency rules
• Gemfile.lock = exact resolved versions
• Run bundle install to generate or update Gemfile.lock
• Usually commit Gemfile.lock for applications
• Often do not commit Gemfile.lock for libraries/gems
• Do not manually edit Gemfile.lock
• Review lock file changes before committing
• If contributing to an existing repo, follow the project's current convention

Quick rule

App? Commit Gemfile.lock
Library? Often ignore Gemfile.lock

Useful commands

bundle install
bundle update
bundle update <gem_name>

Pull request tip

If the repo currently does not include Gemfile.lock, do not add it unless:

• the maintainers expect it, or
• the project is clearly an application and the omission was accidental

Should Gemfile.lock be committed to Git?

Usually yes for Ruby applications, and often no for reusable gems or libraries.

Why did Bundler create Gemfile.lock if it was not in the repo?

Bundler generates it when resolving dependencies during bundle install, even if the file is not committed.

Will adding Gemfile.lock in a pull request cause problems?

It can, if the project intentionally does not track it. Check whether the repository is an app or a library, and follow the existing convention.

Should Gemfile.lock be in .gitignore?

Only if the project has chosen not to commit it, which is more common for libraries than applications.

Can I delete Gemfile.lock?

Yes, but Bundler may resolve different versions the next time dependencies are installed. In an application, that can make behavior less predictable.

Should I edit Gemfile.lock manually?

No. Let Bundler update it through bundle install or bundle update.

How do I know whether a repo is an app or a library?

Look for clues such as a .gemspec file, gem packaging setup, or whether the project is meant to be deployed as an application.

• Bundler: The Ruby dependency manager that creates and uses Gemfile.lock.
• Gemfile: The file where Ruby project dependencies are declared.
• Dependency management: The general practice of installing and tracking external packages.
• Version constraints: Rules like ~> that allow some versions and reject others.
• Reproducible builds: Ensuring the same dependencies are installed across environments.
• Semantic versioning: Helps explain why version ranges and lock files matter.
• .gitignore: Controls which files Git should ignore.
• Ruby gems vs applications: Important for deciding whether Gemfile.lock should be committed.