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Head-to-head · Code Transpilers

Cython vs Scala.js

  • Updated Oct 2026
  • Both researched from official sources
  • 5 checks side by side
Higher score Cython #4 in Code Transpilers 8.7/10 Free plan Free plan✓ 2 of 4 features Visit Cython
Scala.js #8 in Code Transpilers 8.3/10 Open source ✓ 3 of 4 features Visit Scala.js

Cython leads on 0 checks, Scala.js on 1, and 4 are even. Who comes out ahead on the 5 yes/no, price and count checks where we have data for both products. The editor score weighs everything else too.

Our verdict

  • Highest scoreCython · 8.7/10
  • Free planonly Cython
  • Most featuresScala.js · 3 of 4

Cython scores higher on our rubric for code transpilers: 8.7 against 8.3 out of 10; our editors rank them #4 and #8.

Scala.js offers intermediate output; Cython doesn't. On conversion mode, Scala.js gives you Both where Cython offers Source-to-source.

Cython is the better fit for python projects needing C or C++ extensions. Scala.js is the better fit for scala teams building JavaScript applications.

  • Cython fits best

    Python projects needing C or C++ extensions

  • Scala.js fits best

    Scala teams building JavaScript applications

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Side by side

Feature Cython 8.7/10 Visit ↗ Scala.js 8.3/10 Visit ↗
At a glance
Editor score 8.7 8.3
Ranking #4 in Code Transpilers #8 in Code Transpilers
Best for Python projects needing C or C++ extensions Scala teams building JavaScript applications
Pricing model Free Free
Starting price Free plan Open source
Free plan ✓ (best) Not checked yet
Free trial — —
Deployment Self-hosted Self-hosted
Support Community, Docs Community, Docs
Integrations 10 integrations 5 integrations
Built for Solo, Small business, Mid-market, Enterprise Solo, Small business, Mid-market, Enterprise
Features Cython 2/4 · Scala.js 3/4
Syntax-version conversion — Not checked yet
Intermediate output — ✓ (best)
CLI access ✓ ✓
API access ✓ ✓
Specs
Source languages Not checked yet Not checked yet
Target languages Not checked yet Not checked yet
Conversion mode Source-to-source Both
Our review
Pros
  • Translates Python and Cython source into C or C++ code
  • Supports optional static types and C/C++ interoperability
  • Works with Jupyter and build tools including setuptools and Meson
  • Incremental compilation supports iterative Scala-to-JavaScript builds
  • Dead-code elimination and linking help shape JavaScript output
  • Interop includes JavaScript libraries, React, AngularJS, Node.js, and Vite
Cons
  • Requires a native build step to create importable extension modules
  • Focused on Python-to-C/C++ compilation rather than general-purpose conversion
  • Community and documentation are the listed support channels
  • Requires Scala source code, so it is not a general-purpose transpiler
  • Project workflows are commonly managed through build tools such as sbt
  • Support is through community channels and documentation
Our verdict

Cython is an open-source programming language and static compiler for Python developers building compiled extension modules or connecting Python code to C and C++ libraries. It translates Python or Cython source into C or C++ code, which…

Read the review →

Scala.js brings Scala into JavaScript application development by compiling Scala source files into JavaScript. It is aimed at teams that want to write application logic in Scala while targeting browsers, Node.js, or JavaScript modules. The…

Read the review →
  1. CythonCode Transpilers 8.7Free plan
  2. Scala.jsCode Transpilers 8.3Open source

Strengths and trade-offs

  • Cython — where it wins

    • Translates Python and Cython source into C or C++ code
    • Supports optional static types and C/C++ interoperability
    • Works with Jupyter and build tools including setuptools and Meson

    Where it doesn't

    • Requires a native build step to create importable extension modules
    • Focused on Python-to-C/C++ compilation rather than general-purpose conversion
    • Community and documentation are the listed support channels

  • Scala.js — where it wins

    • Incremental compilation supports iterative Scala-to-JavaScript builds
    • Dead-code elimination and linking help shape JavaScript output
    • Interop includes JavaScript libraries, React, AngularJS, Node.js, and Vite

    Where it doesn't

    • Requires Scala source code, so it is not a general-purpose transpiler
    • Project workflows are commonly managed through build tools such as sbt
    • Support is through community channels and documentation
  • Cython8.7/10 · Free plan

    An open-source compiler for Python projects that need native C or C++ extensions.

    Visit CythonFull verdict →
  • Scala.js8.3/10 · Open source

    An open-source Scala-to-JavaScript toolchain with incremental builds and JavaScript interoperability.

    Visit Scala.jsFull verdict →

More comparisons

All code transpilers comparisons → · Full ranking →

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Last updated · How we research and update