Top 10 Ruby on Rails Gems to Consider for Building Web Apps

Photo of Krzysztof Wójcik

Krzysztof Wójcik

Updated Aug 3, 2023 • 9 min read

Ruby on Rails (RoR) is one of the world’s most popular frameworks for web application development.

Its simplicity and efficiency have led to it being described as the ideal ‘startup technology’, and currently over 3.7 million apps are using Ruby on Rails.

The popularity of this framework is largely down to Ruby on Rails gems, which allow for rapid prototyping and testing which really reduce the amount of time you need to spend coding your application, and thus allow you to release new products to market much faster.

Ruby on Rails gems are libraries which allow any developer to add new functionalities without writing code - they’re like plugins, and they’re available for almost every function you could name, from payment processing tools to authentication.

In this article, we’re going to run you through some of the best Ruby on Rails gems you can consider using in your own web app development process. Each of these will make your development process easier and can perform different functions depending on what your project needs. By the end of this article, you’ll understand more about the features of the top ten RoR gems for Ruby and what they can and can’t achieve for your web app.


Pry operates as a meta plugin or library. Often when developers are trying to integrate libraries in Ruby on Rails, some gems return errors or encounter bugs due to inappropriate integration. Pry is great in these situations as it is used for debugging such errors and helps to eliminate the problem of binding different gems from different libraries.

Some of its features include syntax highlighting, run git, start editors, command shell integration and a very resilient and powerful command system. These features allow you or your developers the ability to set specified breakpoints and implement code debugging on a step-by-step basis.


Devise is used for simplifying the process of authentication. If, for example, you’re creating an application on one of the social media networks or building an eCommerce solution, the developer will need to provide authorization and authentication for the particular application.

Some developers prefer to use their own code to do this, but you can also do it in Ruby, and Devise is the perfect gem for the task. Devise is one of the best Ruby on Rails gems - it includes 20+ modules, such as Omniauthable, Database Authenticatable, Registrable, Confirmable, Trackable, Recoverable, Lockable, Timeoutable, Rememberable, FriendlyId, and Validatable.


Pundit is a Ruby on Rails gem that processes authorization via a simple API. It’s important here to remember that authorization is not the same as authentication: authentication means verifying that you are who you say you are, whereas authorization involves verifying that you have permission to perform an action.

In the process of authorization, a device will look at a user’s credentials to ensure the client they’re using is allowed to take certain actions or access certain features. Pundit works within this cycle and allows you to restrict certain parts of your application to approved users.


Amongst Ruby on Rails gems, Sidekiq is one of the most commonly used tools for background processing. It is supported by the Redis library - an in-memory key-value store admired for its flexibility and performance - and uses it as a job management store.

A lot of developers like Sidekiq because it has multithreading capabilities which enhance its speed, making background processing much faster and simpler for your developers.


RSpec is another extremely popular Rails Gem, and is a great tool for writing unit test cases, mainly in BDD or TDD environments. Unit testing is a software testing method in which single units of source code are checked to verify that they’re fit for purpose.

RSpec’s clear syntax allows you to write unit tests as close to human language as possible and is very efficient in testing the behaviour of particular models or libraries. Its main benefit is that it is simple to use and can be executed by installing the config files or spec helpers.

Factory Bot

Factory Bot, sometimes also referred to by its original name, Factory Girl, is a software library for Ruby on Rails which provides factory methods to create test fixtures for automated software testing.

The fixture objects can be created on the fly; they may be plain Ruby objects with a predefined state, ORM objects with existing database records or mock objects.

Factory Bot essentially provides fake data so you can run test cases, which makes the testing process simpler and quicker, removing the need for time-consuming and error-prone manual data entry.


Similar to Factory Bot, Faker is used to easily create fake data, including names, addresses and phone numbers, for use in testing. The difference is that while Factory Bot sets up Ruby objects for use as test data, Faker actually creates fake data automatically.

These are two gems which work well together. As Drifting Rubyexplains it: ‘Factory Bot is a fixtures replacement which can generate the needed records directly in the tests. Faker can be used to create fake data for these records’. Again, Faker’s main benefit is that it will save you a huge amount of time in testing and is simple to use.


Kaminari is possibly the most popular of all gems for Ruby developers, as it has over 5 million downloads on Github. Kaminari is a Scope & Engine based, clean, powerful, agnostic, customizable and sophisticated paginator for Rails 3+. Pagination is used in some form in almost every web application to divide returned data and display it on multiple pages within one web page.

Pagination also includes the logic of preparing and displaying the links to the various pages. Pagination can be handled client-side or server-side. It was developed by Akira Matsuda along with Yuki Nishijima, Zachary Scott, Hiroshi Shibata in 2011, and the name Kaminari comes from the Japanese word for ‘thunder’.


SimpleCov is a code coverage analysis tool for Ruby. It uses Ruby's built-in Coverage library to gather code coverage data, but makes processing its results much easier by providing a clean API to filter, group, merge, format, and display those results, giving you a complete code coverage suite that can be set up with just a couple lines of code.

In most applications, you will probably want overall coverage results for your projects, including various tests. SimpleCov takes care of this automatically by merging and caching results when generating reports, so your report actually includes coverage across your test suites and thereby gives you a better picture of blank spots.


Another famous Ruby gem is Rubocop, a popular tool for analyzing code quality in rails development. In web development, it ensures that the application’s code matches the Ruby Style Guide for writing the best program.

Any style issues are reported in the command line, leaving no margin for breaching the Ruby code writing style. One of the best things about RuboCop is that it fixes simple errors on its own, such as line breaks, syntax highlighting, gaps, and more.

Add new functionalities with Ruby on Rails gems

This list has highlighted just a few of the top Ruby on Rails gems for building web apps and other software development projects. Keep in mind that this is a subjective list based on our experience with RoR gems. However, there are actually thousands more gems to choose from - 165,052 in fact, by the latest estimate - and this variety of gems makes theRUby programming language one of the most versatile around, helping you save time and money in your application development process.

Using the gems listed here, as well as other Ruby gems, you can build custom rails apps to suit any business need and enable rapid software development to achieve faster time to market and stay competitive. With this variety of gems and plugins, Rails can be used for almost any project and by most developers at any level of skill or stage of learning.

Without these gems, Rails developers could struggle. Luckily, there are plenty of them out there, and using the top gems, such as those listed here, is common practice, when developing web applications. To learn more about the different Ruby gems on offer and how they can be used to help your business, get in touch to speak to a Netguru development expert today.

Photo of Krzysztof Wójcik

More posts by this author

Krzysztof Wójcik

Krzysztof works as a Ruby on Rails Team Leader at Netguru.
Codestories Newsletter  Check what has recently been hot in European Tech.   Subscribe now

We're Netguru!

At Netguru we specialize in designing, building, shipping and scaling beautiful, usable products with blazing-fast efficiency
Let's talk business!

Trusted by: