Web API for code compilation and execution.
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.github Changed Dockerfiles and Compose files to use always latest image Apr 23, 2017
app Updated default configuration variables cpu_time_limit memory_limit a… Sep 30, 2017
bin Separated API Jan 27, 2017
config Created Sessions and Info controllers Sep 30, 2017
db Added support for OCaml 4.05.0 Sep 30, 2017
docs/api Updated API docs for v1.0.0 and added new favicon Oct 1, 2017
lib/tasks Added support for new languages Sep 26, 2017
log Separated API Jan 27, 2017
public Updated default values in dummy client Oct 1, 2017
scripts Use wide documentation format Sep 30, 2017
spec Added support for OCaml 4.05.0 Sep 30, 2017
tmp Separated API Jan 27, 2017
vendor Separated API Jan 27, 2017
.dockerignore Added support for API authentication Sep 16, 2017
.gitignore Added judge0-api.conf to gitignore Sep 16, 2017
.rspec Separated API Jan 27, 2017
.rubocop.yml Added CodeClimate files Sep 12, 2016
Dockerfile Changed version label in Dockerfile Oct 1, 2017
Dockerfile.dev Changed configuration and Dockerfiles and added support for plain text Sep 26, 2017
Gemfile Created authorized index route for submissions Sep 22, 2017
Gemfile.lock Changed configuration and Dockerfiles and added support for plain text Sep 26, 2017
LICENSE Updated API docs Feb 4, 2017
README.md Added news annoucement about Judge0 API 2.0.0 Mar 3, 2018
Rakefile Separated API Jan 27, 2017
config.ru Separated API Jan 27, 2017
docker-compose.dev.yml Changed configuration and Dockerfiles and added support for plain text Sep 26, 2017
docker-compose.prod.https.yml API service should also be privileged because of wait parameter Oct 1, 2017
docker-compose.prod.yml API service should also be privileged because of wait parameter Oct 1, 2017
judge0-api.conf.default Updated default configuration variables cpu_time_limit memory_limit a… Sep 30, 2017


[NEWS] Please read this blog post (1 min read) before continuing.

Judge0 API

License: GPL v3 Donate


Judge0 API is an web API for code compilation and execution. Complete and detailed API documentation is available on https://api.judge0.com.


  1. Supported Languages
  2. Project Organization
  3. Quick Development Setup
  4. Quick Production Setup
  5. About Docker Images
  6. Adding New Compiler or Interpreter
  7. HTTPS In Production
  8. Notes

Supported Languages

# Name
1 Bash (4.4)
2 Bash (4.0)
3 Basic (fbc 1.05.0)
4 C (gcc 7.2.0)
5 C (gcc 6.4.0)
6 C (gcc 6.3.0)
7 C (gcc 5.4.0)
8 C (gcc 4.9.4)
9 C (gcc 4.8.5)
10 C++ (g++ 7.2.0)
11 C++ (g++ 6.4.0)
12 C++ (g++ 6.3.0)
13 C++ (g++ 5.4.0)
14 C++ (g++ 4.9.4)
15 C++ (g++ 4.8.5)
16 C# (mono
17 C# (mono
18 Clojure (1.8.0)
19 Crystal (0.23.1)
20 Elixir (1.5.1)
21 Erlang (OTP 20.0)
22 Go (1.9)
23 Haskell (ghc 8.2.1)
24 Haskell (ghc 8.0.2)
25 Insect (5.0.0)
26 Java (OpenJDK 9 with Eclipse OpenJ9)
27 Java (OpenJDK 8)
28 Java (OpenJDK 7)
29 JavaScript (nodejs 8.5.0)
30 JavaScript (nodejs 7.10.1)
31 OCaml (4.05.0)
32 Octave (4.2.0)
33 Pascal (fpc 3.0.0)
34 Python (3.6.0)
35 Python (3.5.3)
36 Python (2.7.9)
37 Python (2.6.9)
38 Ruby (2.4.0)
39 Ruby (2.3.3)
40 Ruby (2.2.6)
41 Ruby (2.1.9)
42 Rust (1.20.0)
43 Text (plain text)

Project Organization

Judge0 API is a Rails 5 application organized in two major components:

  • Rails API
    • accepts requests and creates background jobs for Worker.
  • Worker
    • accepts new jobs and process them as they arrive. Worker has only one job - IsolateJob, that job runs untrusted programs in sandboxed environment.

Quick Development Setup

Setting up your development environment is easy thanks to Docker and Docker Compose. So please install those before continuing.

Because we are running our development environment in Docker you don't need to have Ruby, Rails, PostgreSQL, Redis, etc. installed on your computer. You just need to:

  1. Pull judge0/api image:
    $ docker pull judge0/api
  2. Copy judge0-api.conf.default to judge0-api.conf.
  3. Run development shell (it will take a while only first time):
    $ ./scripts/dev-shell
  4. Create, migrate and seed the database:
    $ rails db:setup

scripts/dev-shell script will open you new development shell always in the same container, and if container doesn't exist it will create one for you.

You need to run Rails API and Worker in order to have Judge0 API fully operational:

  1. Open new development shell and in there run Rails API server:
    $ ./scripts/dev-run-server
  2. Open new development shell again and in there run Worker process:
    $ ./scripts/dev-run-worker
  3. Open http://localhost:3000 in your browser.

This is minimal setup for development environment, now you can open your favorite editor in your host and start developing Judge0 API.

Quick Production Setup

To host your own Judge0 API you need to install Docker and Docker Compose on your server and after you are done proceed with the following:

  1. Copy docker-compose.prod.yml on your server and save it as docker-compose.yml

    $ wget https://raw.githubusercontent.com/judge0/api/master/docker-compose.prod.yml -O docker-compose.yml
  2. Save judge0-api.conf.default to your server as judge0-api.conf

    $ wget https://raw.githubusercontent.com/judge0/api/master/judge0-api.conf.default -O judge0-api.conf
  3. In judge0-api.conf change RAILS_ENV to production.

  4. Run database:

    $ docker-compose up -d db
  5. Run all other services:

    $ docker-compose up -d
  6. Open http://<IP OF YOUR SERVER>:3000 in your browser.

About Docker Images

This project has two Dockerfiles:

  1. Dockerfile

    • builds judge0/api:latest image
  2. Dockerfile.dev

    • build judge0/api:dev image

judge0/api:latest is built FROM judge0/api-base:latest image which contains installed compilers and sandbox environment. This image represents production image of Judge0 API.

judge0/api:dev is your local development image built FROM judge0/api:latest. It is not pushed to Docker Hub. That is why you first need to pull judge0/api:latest before building your development environment.

Adding New Compiler or Interpreter

To add new compiler or interpreter you first need to install it into Judge0 API Base image. Instructions on how to do that can be found in documentation for Judge0 API Base.

After you have added your favorite compiler/interpreter to Judge0 API Base image you need to define how this compiler/interpreter is used. This is done in db/seeds.rb file.

You have four attributes:

  • name - name of your language you are supporting, include also compiler name and version
  • source_file - in what file should user's source code be saved before it is compiled
  • compile_cmd - how this file is compiled, interpreted languages won't have this attribute
  • run_cmd - how should we run this compiled or interpreted language

We already provided enough examples for most common languages, be sure to check that out.

HTTPS In Production

To use HTTPS in production we are going to use https://letsencrypt.org/.

You need to have your own domain for this to work. Just use docker-compose.prod.https.yml insted of docker-compose.prod.yml and change VIRTUAL_HOST, LETSENCRYPT_HOST and LETSENCRYPT_EMAIL variables.

Everything else you need to do is described in Quick Production Setup section.


Judge0 API is simple to use and develop only if you are comfortable with using Docker and Docker Compose.

Docker and Docker Compose allow us to get rid of all dependencies, and concentrate on what is important - features, functionality and reliability.

Please before working with Judge0 API project, make yourself comfortable with Docker and Docker Compose, because we are using it extensively.

We will add extensive documentation in the future about how and why we are using Docker and Docker Compose here, but this documentation won't substitute your knowledge of this technologies.

Feel free to ask us any questions in Issues directly. :)


If you like Judge0, please consider making a donation to support this project.