Does this send my code anywhere?

No. Compilation runs entirely in your browser using the official `coffeescript` npm package.

Is the output identical to the CoffeeScript CLI's output?

Yes, it uses the same compiler package the `coffee` command line tool is built on.

Does it support the full CoffeeScript language, or just a subset?

The full language, classes, comprehensions, string interpolation, the existential operator, and everything else CoffeeScript supports, since it calls the same `CoffeeScript.compile()` function the official CLI uses. The only real limitation is that it compiles one pasted snippet, not a multi-file project with `require`-based imports.

What does the `bare` option actually change?

Without it, CoffeeScript wraps compiled output in a top-level anonymous function to keep declared variables out of the global scope. With `bare: true`, which this tool uses, that wrapper is omitted, so top-level `var` declarations sit directly in the output, the same as running `coffee --compile --bare`.

CoffeeScript Compiler - Compile CoffeeScript to JavaScript Online

Overview

Introduction

CoffeeScript compiles down to JavaScript, but seeing exactly what a snippet expands to usually means running a local build.

This tool compiles CoffeeScript to JavaScript directly in your browser using the official compiler.

What Is CoffeeScript Compiler?

A CoffeeScript-to-JavaScript compiler using the same `coffeescript` package that powers the official `coffee` CLI.

It compiles with the `bare` option, so the output isn't wrapped in an IIFE.

How CoffeeScript Compiler Works

The compiler parses CoffeeScript's indentation-based syntax and emits equivalent JavaScript.

A syntax error reports the line and column where compilation failed.

When To Use CoffeeScript Compiler

Use it to see exactly what JavaScript a piece of CoffeeScript compiles to, useful when debugging or migrating away from CoffeeScript.

It's also useful when migrating a CoffeeScript codebase to plain JavaScript, since you can compile file by file and review the generated JS before committing it.

Often used alongside TypeScript Compiler and JavaScript Formatter.

Features

Advantages

Runs entirely client-side.
Uses the official compiler, so output matches the `coffee` CLI exactly.
Reports the exact line and column of a syntax error, which is useful given how much CoffeeScript's syntax relies on indentation.

Limitations

Doesn't support multi-file compilation or CoffeeScript's require-based module resolution, since it compiles a single pasted snippet.

Examples

Simple function

Input

greet = (name) ->
  "Hello, #{name}!"

Output

var greet;

greet = function(name) {
  return `Hello, ${name}!`;
};

Implicit returns and string interpolation are compiled to their explicit JavaScript equivalents.

Best Practices & Notes

Best Practices

Use this to understand generated output while migrating a CoffeeScript codebase to plain JavaScript or TypeScript.
Compile small pieces at a time when migrating a larger file; it's easier to verify each generated JS chunk against the original CoffeeScript.

Developer Notes

Uses `CoffeeScript.compile(input, { bare: true })` from the official `coffeescript` package, dynamically imported.

CoffeeScript Compiler Use Cases

Understanding what a CoffeeScript snippet compiles to
Converting a small CoffeeScript file to JavaScript during a migration

Common Mistakes

Pasting a snippet that relies on CoffeeScript's implicit module wrapper and expecting identical behavior once bare-compiled.
Forgetting that CoffeeScript returns the value of the last expression in a function automatically; a plain JavaScript rewrite of that code needs an explicit `return`.

Tips

If compilation fails, CoffeeScript's indentation-based syntax means a single misplaced space is often the cause; check the reported line closely.
Compare the compiled output side-by-side with the original CoffeeScript to build intuition for how comprehensions and implicit returns map to explicit JavaScript.

CoffeeScript Compiler