Opal

At a glance

• Editor score
  7.6 / 10
• Pricing
  Free plan
• Best for
  Ruby developers bringing code to JavaScript
• Free plan
  Yes
• Paid from
  Free
• Conversion mode
  Source-to-source
• Facts checked
  22 Sep 2026

• Where it wins

  • Compiles Ruby to JavaScript from the command line or at runtime
  • Includes Ruby core and standard-library implementations
  • Supports interoperability, source maps, and Ruby dependency loading

• Where it doesn't

  • Ruby library coverage is described as much of the core and standard library
  • Community and documentation are the listed support channels
  • Integration examples focus on Rails and Rack

Our verdict on Opal

Opal gives Ruby developers a route to run Ruby code in JavaScript-hosted software, including client-side web applications and Node.js projects. It is a source-to-source compiler, not a hosted application service: the project is open source under the MIT license, with command-line and API access. Its audience is developers who want to bring Ruby code into JavaScript environments and are comfortable working with a compiler and its ecosystem rather than choosing a managed conversion service.

The standout feature is the combination of Ruby support and two-way interoperability. Opal includes implementations of much of Ruby’s core library and standard library, and Ruby code can interact with JavaScript while JavaScript can also interoperate with Ruby. Developers can compile ahead of time or compile Ruby at runtime through opal-parser. Source-map generation and dependency loading through the Opal load path add useful pieces for application development. The library coverage is substantial in scope, but the description does not claim complete Ruby compatibility, so projects relying on specific Ruby behavior should assess that fit before committing.

Opal also has examples for Rails and Rack integration, with Sprockets among its listed integrations, making it relevant to Ruby web development workflows that target JavaScript. It is free and open source, with community and documentation listed as support channels rather than paid service tiers. Choose Opal when Ruby-to-JavaScript compilation and interoperability are central to the work; it is less suited to teams seeking a hosted service, a managed support relationship, or a tool presented as a complete implementation of every Ruby library.

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Opal pricing

Opal fact sheet

Opal integrations

Opal lists 3 integrations on its own site.

• Rails
• Rack
• Sprockets

Alternatives to Opal

• BabelFlexible ECMAScript transforms with CLI, Node.js APIs, and browser compilation.9.3
• SWCAn open-source compiler with minification and bundling for JavaScript and TypeScript workflows.9.2
• Kotlin/JSA free Kotlin-to-JavaScript toolchain for browser and Node.js projects.8.8

See all Opal alternatives →

Featured on iTechGuides

Opal is listed in our Code Transpilers directory. Add the badge to your site — it links back to this page.

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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

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Last updated 7 Oct 2026 · How we research and update