Upgrading a Ruby on Rails application can feel overwhelming, especially when you are unsure whether to move straight to the latest version or take a gradual path. With multiple dependencies, evolving frameworks, and live users relying on stability, an upgrade is never just a technical task. It is a strategic exercise that demands clarity, preparation, and careful execution.
This guide walks through the entire Rails upgrade journey, from early planning to deployment and performance validation, so you can move forward with confidence and avoid costly surprises.
What should you evaluate before upgrading a Ruby on Rails application?
Upgrading an actively used application introduces risk if it isn’t approached methodically. A thoughtful evaluation phase helps you surface potential blockers early and design a smoother transition.
Before starting, review the current Rails and Ruby versions your application is running on and compare them with your intended target versions. Identify deprecated APIs, behaviour changes, and removed features that could affect your codebase. It’s equally important to assess whether all third-party gems and libraries have compatible releases available.
In parallel, define a backup and rollback strategy to protect production data, and ensure your testing environment mirrors real-world usage as closely as possible. A well-planned pre-upgrade assessment significantly reduces downtime and unexpected regressions later in the process.
What are the key steps in upgrading a Ruby on Rails application?
Step 1: Review the current state of the application
Start by analysing your existing codebase in detail. Look for deprecated syntax, outdated patterns, and areas where Rails behaviour has changed across versions. Pay special attention to controllers, background jobs, view rendering, and database interactions.
Third-party dependencies also deserve careful review. Some gems may require upgrades, replacements, or complete removal to remain compatible with newer Rails versions. This evaluation sets a realistic baseline and helps you estimate the scope of work involved.
Beyond compatibility, this step ensures your application is ready to benefit from newer Rails improvements in performance, security, and maintainability.
Step 2: Research and plan the upgrade path
Once the current state is clear, research the latest stable versions of Ruby and Rails. Study official release notes, changelogs, and upgrade guides to understand what’s changed and what actions are required.
From this research, create a structured upgrade plan that outlines tasks, risks, and dependencies. Decide whether the upgrade will involve only Rails, only Ruby, or both. This planning phase is critical—it determines the complexity, timeline, and overall stability of the upgrade.
Should you upgrade Ruby and Rails together or separately?
If your Ruby version is outdated or no longer supported, upgrading Ruby alongside Rails is usually the safest choice. However, if Ruby is already on a stable, supported version, you may choose to upgrade Rails alone to reduce complexity.
Upgrading both at once can save time long-term, but it often introduces more variables. The decision should be based on your application’s size, dependency stack, and tolerance for change.
Do you need data or structural migrations?
Framework upgrades sometimes require changes to how data is stored or managed. This often happens when older gems or custom solutions are replaced by newer, built-in Rails features.
For example, applications that previously relied on third-party file upload libraries may need to migrate to newer Rails-native alternatives. These transitions require careful data handling to preserve integrity and avoid downtime.
Direct upgrade vs phased upgrade: which is better?
A direct upgrade jumps straight from the current version to the latest release. While faster, it carries higher risk—especially for large or complex applications.
A phased upgrade moves incrementally through intermediate versions. This approach allows for controlled testing, easier debugging, and better stability. Larger applications typically benefit from phased upgrades, while smaller apps with minimal version gaps may safely opt for a direct jump.
Step 3: Update the Ruby version
Keeping Ruby up to date is essential for long-term security and stability. Before changing versions, confirm that your application and dependencies support the new Ruby release.
Use a version manager such as RVM, rbenv, or asdf to install and manage multiple Ruby versions. These tools allow seamless switching between versions without affecting your system setup.
In most Rails projects, the Ruby version is defined in:
- The Gemfile
- The .ruby-version file
Updating both ensures consistency across development, testing, and production environments.
Step 4: Update the Rails version
After upgrading Ruby, move on to Rails. Update the Rails version specified in your Gemfile to the desired release.
You can either edit the version manually or use Bundler commands to fetch compatible updates. Once complete, install updated dependencies and resolve any version conflicts that arise.
This step often reveals deprecated APIs or configuration changes that must be addressed before proceeding further.
Step 5: Update application configuration
Rails upgrade frequently introduce configuration changes. Review the official upgrade guide for your target version and adjust your application accordingly.
Rails provides tools to help update default configuration files, making it easier to align your app with the new version’s standards. Running the built in configuration update command allows you to compare old and new defaults and selectively apply changes.
For deeper insight into configuration differences between versions, tools that compare Rails defaults across releases can be extremely useful, especially when upgrading across multiple major versions.
Step 6: Replace deprecated dependencies
As Rails evolves, some gems become obsolete or unsupported. Identify outdated dependencies early and replace them with actively maintained alternatives.
Updating dependencies not only improves compatibility but also strengthens security and performance. Regular dependency maintenance reduces technical debt and ensures your application remains resilient over time.
Step 7: Review Asset Pipeline configuration
The Asset Pipeline plays a key role in managing CSS, JavaScript, and image assets. During an upgrade, verify that existing assets remain compatible with the newer Rails version.
Check configuration files, asset helpers, and build processes to ensure everything functions correctly. Newer Rails versions often introduce improvements to asset handling that can enhance performance when properly configured.
Step 8: Test the application thoroughly
Testing is the backbone of a successful upgrade. After updating code and configurations, validate the application through multiple layers of testing.
Unit testing ensures individual components behave as expected. Strengthen coverage around core features and critical workflows.
Regression testing confirms that existing functionality continues to work after the upgrade, helping catch unintended side effects.
Performance testing evaluates response times, scalability, and resource usage. Load-testing tools can simulate real-world traffic and expose bottlenecks.
Security testing identifies vulnerabilities introduced during the upgrade and ensures compliance with modern security standards.
Step 9: Deploy and monitor
Once testing is complete, deploy the upgraded application to staging or production. Monitor closely for errors, performance regressions, or unexpected behaviour.
Application monitoring and error-tracking tools allow you to detect issues early and respond before users are affected. Proactive monitoring is especially important in the first few days after deployment.
How do you validate performance after a Rails upgrade?
Upgrading Rails introduces internal changes that can impact performance in subtle ways. Validation ensures the application not only works correctly but also performs efficiently under real-world conditions.
Post-upgrade performance checks should include response times, database query efficiency, memory usage, and scalability under load. Comparing metrics from before and after the upgrade helps confirm whether the new version delivers measurable improvements—or highlights areas needing optimisation.
Treat performance validation as a mandatory final step, not an optional one. It safeguards user experience and protects the value of the upgrade investment.
