Educational computer programming environment using Haskell
Clone or download
Pull request Compare This branch is 31 commits ahead, 469 commits behind google:master.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.


CodeWorld is an educational environment using Haskell. It provides a simple mathematical model for geometric figures, animations, and interactive and multi-player games. The web-based programming environment supports this educational mission with a zero-setup editor and compiler, easy sharing and cloud storage of projects, and the ability to run programs right in the web browser using GHCJS.

There are several variants of CodeWorld available:

  • CodeWorld uses an educational variant of the Haskell language and libraries, designed to support mathematics instruction.
  • CodeWorld Haskell is built against standard Haskell instead of the educational variant, to build programs which can either be on the web site with GHCJS, or compiled natively with the codeworld-api package and blank-canvas.
  • CodeWorld Blocks provides a drag-and-drop programming user interface for younger students to build programs with CodeWorld.


CodeWorld is stable and has been used in schools for years! See the users page for a partial list. We're constantly improving the environment, though. Breaking changes, when necessary, are scheduled to occur between typical (U.S.) K-12 school semesters, to minimize disruption of existing classes.

Google is distributing the code for CodeWorld, but CodeWorld is not an official Google project, and Google provides no support for it. Instead, questions about the project or code should be asked to the codeworld-discuss mailing list. A student-friendly question and answer forum is also available at for questions about programs written using CodeWorld, rather than questions about building or modifying CodeWorld itself.

Getting Started

Just visit to get started.

There is no need to download or install anything to use CodeWorld. This repository will be useful if you prefer to fork and modify the CodeWorld environment, or contribute changes.

Discuss and Learn More

To discuss and hear announcements about CodeWorld, subscribe to the mailing list at!forum/codeworld-discuss

The mailing list should be used to:

  • Hear announcements about and discuss upcoming changes and features.
  • Ask questions about using the system, and give feedback about your experiences.
  • Share interesting ways of using the site, related classroom activities, and more.

To report bugs or file formal feature requests, try


There is a slight bit of paperwork involved in contributing to CodeWorld. You'll need to agree to a Contributor License Agreement. See for details.

Build and Deployment

Building and running CodeWorld can be a lengthy process, but is automated using the installation scripts in the root directory, which work on most forms of Linux, including Debian, Ubuntu, RedHat, and CentOS. The step by step instructions are as follows:

  1. Read the caveats, explained below.
  2. Change to the root directory of the project.
  3. Run ./ to set up the project.
  4. Run ./ to start the server.

You can now access the CodeWorld system at http://localhost:8080.

If you make changes to CodeWorld, you can rebuild it without rebuilding the dependencies:

  1. Change to the root directory of the project.
  2. Run ./ to recompile just CodeWorld itself, using previously installed tools and libraries.
  3. Run ./ to start the server.


Leaky GHCJS Sandboxing

While the installation process installs most of its files inside codeworld/build, it does clobber ~/.ghc, ~/.ghcjs, and ~/.cabal. I recommend that you run CodeWorld as a dedicated user account to avoid causing problems for other Haskell installations. If you don't, note that you will lose your user package database.

See bug #4 for details.

Google API Key

CodeWorld allows users to authenticate using a Google account, and save their projects. For this feature to work, you need to obtain a Google API key, and store it in web/clientId.txt. If you don't do this, the sign-in and save features will not function correctly, but the rest of the site will be usable.

Swap Space

If you are installing CodeWorld on a virtual server, be aware that the default RAM on these servers is often not sufficient for GHC. CodeWorld needs to compile very large Haskell projects during its installation. The following should be sufficient to resolve any out-of-memory problems you encounter:

$ sudo dd if=/dev/zero of=/swap bs=1024 count=2097152
$ sudo mkswap /swap
$ sudo swapon /swap

This creates a 2 GB swap file to increase available virtual memory. Installation with a swap file may be slow, but it will succeed. (Unless you intend to write very large programs in CodeWorld, it's usually safe to remove the swap file after running the server for the first time.)