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4.3.3 • Public • Published

JavaScript interface for MiniZinc

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This package provides a JavaScript API for MiniZinc for use in web browsers using WebAssembly, or in NodeJS using a native installation of MiniZinc.

This library powers the MiniZinc Playground.

Getting started

Using a CDN (recommended)

Using ECMAScript modules:

<script type="module">
  import { Model } from '';
  const model = new Model();
  model.addFile('test.mzn', 'var 1..3: x;');
  const solve = model.solve({
    options: {
      solver: 'gecode',
      'all-solutions': true
  solve.on('solution', solution => {
  solve.then(result => {

Using a traditional script:

<script src=""></script>
  const model = new MiniZinc.Model();
  model.addFile('test.mzn', 'var 1..3: x;');
  const solve = model.solve({
    options: {
      solver: 'gecode',
      'all-solutions': true
  solve.on('solution', solution => {
  solve.then(result => {

Self-hosting WebAssembly files

If you're using a bundler, you can add the library to your project:

npm install minizinc

Then import it with:

import * as MiniZinc from 'minizinc';

These three files need to be served by your webserver (found in node_modules/minizinc/dist):

  • minizinc-worker.js
  • minizinc.wasm

If you place them alongside your bundled script, they should be found automatically. Otherwise, their URLs can be specified during initialisation.

In NodeJS

This requires an existing installation of MiniZinc.

Add the library with:

npm install minizinc

Then import it with:

// If using ESM
import * as MiniZinc from 'minizinc';
// If using CommonJS
const MiniZinc = require('minizinc');

If you have added MiniZinc to your PATH, it will be found automatically. Otherwise, you can specify the executable path during initialisation.



Initialisation happens automatically when the library is used, or by calling init(...). This can be used to ensure that the WebAssembly files start loading immediately, or to specify a different URL for the worker (or path to the MiniZinc executable if using NodeJS).

In the browser:

  // If omitted, searches for minizinc-worker.js next to the minizinc library script
  workerURL: 'http://localhost:3000/path/to/my-own-worker.js',
  // If these are omitted, searches next to the worker script
  wasmURL: 'http://localhost:3000/path/to/minizinc.wasm',
  dataURL: 'http://localhost:3000/path/to/'
}).then(() => {

In NodeJS:

  // Executable name
  minizinc: 'minizinc',
  // Search paths (can omit to use PATH)
  minizincPaths: ['/home/me/.local/bin', '/usr/local/bin']

By default, the NodeJS version tries to find MiniZinc on your PATH.

Creating Models

The main entrypoint for using the library is through the Model class:

const model = new MiniZinc.Model();
// Add a file with a given name and string contents
model.addFile('test.mzn', 'var 1..3: x; int: y;');
// If you're using NodeJS, you can add files from the filesystem directly
// Add model code from a string
model.addString('int: z;');
// Add data in DZN format
model.addDznString('y = 1;');
// Add data from a JSON object
model.addJSON({z: 2});


Solving is done using the Model.solve(...) method, which takes an object with options in .mpc format.

const solve = model.solve({
  options: {
    solver: 'gecode',
    'time-limit': 10000,
    statistics: true
// You can listen for events
solve.on('solution', solution => console.log(solution.output.json));
solve.on('statistics', stats => console.log(stats.statistics));
// And/or wait until complete
solve.then(result => {

During solving, MiniZinc emits events which can be subscribed to/unsubscribed from using the SolveProgress.on / methods. The events are those which appear in Machine-readable JSON output format, with the addition of the exit event, which can be used to detect when solving finishes (if you do not wish to await the SolveProgress object).

By default, --output-mode json is used, allowing you to retrieve the model variable values directly from the solution objects. Use Model.solve({ jsonOutput: false, ...}) (and optionally specify a different output-mode in the options) to disable this behaviour.


For more detailed documentation of all available options and functionality, visit the API documentation.


Compiling MiniZinc for WebAssembly

The WebAssembly build of MiniZinc requires Emscripten.

# Clone MiniZinc
git clone minizinc

# Download solvers (or you can build them yourself using emscripten)
cd minizinc
MZNARCH=wasm ./download_vendor

# Configure MiniZinc
emcmake cmake -S . -B build \
  -DGecode_ROOT="$PWD/vendor/gecode" \
  -DOsiCBC_ROOT="$PWD/vendor/cbc" \
  -DCMAKE_PREFIX_PATH="$PWD/vendor/highs/lib/cmake/highs:$PWD/vendor/chuffed/lib/cmake/chuffed" \

# Build MiniZinc
cmake --build build --config Release --target install

The WebAssembly build of MiniZinc can also be obtained from the build workflow as the minizinc artifact.

Building MiniZinc JS

  1. Run npm install to install dependencies.
  2. Place the bin/ folder of the WebAssembly build of MiniZinc inside this directory. Alternatively set the MZN_WASM_DIR environment variable to the installation directory of the WebAssembly build of MiniZinc.
  3. Run npm run build to build the package. The built files are in the dist/ directory.
  4. Run npm run docs to build the documentation. The output files are in the docs/ directory.


When testing, the web-worker library is used to emulate Web Worker support in NodeJS. This allows us to test both the browser version using WebAssembly, as well as the native version.

Run npm test to run tests using Jest.


This library is distributed under the Mozilla Public License Version 2.0. See LICENSE for more information.




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