Recommended Plan for Migrating from React.js To Opal Ruby & Glimmer DSL for Web

In a recent team retrospective meeting at my job, 5 team devs (all) voted for the future plan item "More use of Opal Ruby & Glimmer DSL for Web in the Rails Web App Frontend". 

We are following a gradual rollout plan for migrating our React.js Frontend to Opal Ruby & Glimmer DSL for Web inside our Fintech Ruby on Rails web application:

• Step 1: Use Opal/Glimmer in new Admin UI features
• Step 2: Use Opal/Glimmer in new Manager UI features
• Step 3: Use Opal/Glimmer in new Customer UI features
• Step 4: Rewrite all legacy React components with Glimmer DSL for Web (either whenever touching legacy React components to make fixes/changes or in an incremental planned fashion that can be spaced out over a period of time with other business priorities taking precedence)

The plan could be adjusted to have as many steps as your web application has user roles with their own groups of webpages that they use, expanding gradually from migrating the least used webpages (lowest risk) to migrating the most used webpages (highest risk).

Step 1 in the process, using Glimmer DSL for Web in the Admin UI, was a success! So, the aforementioned retrospective item was about progressing further into Step 2 in 2026.

Glimmer improved performance in one re-written React page by 33% while cutting its code overall by about ~50% (and the component code became 1/10 what it was given there is no state management code in Glimmer components). 

One other 32-line Glimmer component was reused on 7 Admin UI pages very effectively and its performance of rendering was instant (aka fast enough). 

Also, when a relatively new Software Engineer on the team used Glimmer DSL for Web for the first time, he was able to complete his work in less than a week with much less code than what React.js would have needed, and with much better readability and maintainability. I was really impressed by the work of that Software Engineer in Opal Ruby & Glimmer DSL for Web. 

Eventually, that same developer ended up building another Admin UI feature in Glimmer DSL for Web, and his code was pure poetry! Such small components that don't exceed 43 lines of code.

Part of the reason why Step 4 is recommended at the end of the migration plan is because it is much cheaper to maintain Glimmer Ruby code compared to React JavaScript code. Also, I noticed that I could rewrite a very complicated React component that probably took a week or multiple weeks to build in only about 1-2 days tops, and the overall code gets cut by about half. In other words, it is faster and cheaper to rewrite React components in Glimmer than to maintain them as they are when making fixes and changes. We literally feel like we're flying in Glimmer compared to moving like a slug in React.

This is the true state of the art in Ruby on Rails Frontend Development in 2025 (not silly Inertia that thinks inside the box of JavaScript by enabling more of the same garbage code in React.js/inferior-JavaScript-frameworks).

The future of Frontend Development in Ruby on Rails is very bright!!! I can't wait for what 2026 will bring!