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How to Contribute

Reporting Issues

Please see our FAQ for common issues that people run into.

Should you run into other issues with the project, please don't hesitate to let us know by filing an issue! In general we are going to ask for an example of the problem failing, which can be as simple as a jsfiddle/jsbin/etc. We've put together a jsfiddle template to ease this. (We will keep this link up to date as new releases occur, so feel free to check back here)

Pull requests containing only failing tests demonstrating the issue are welcomed and this also helps ensure that your issue won't regress in the future once it's fixed.

Documentation issues on the site should be reported on handlebars-site.

Pull Requests

We also accept pull requests!

Generally we like to see pull requests that

  • Maintain the existing code style
  • Are focused on a single change (i.e. avoid large refactoring or style adjustments in untouched code if not the primary goal of the pull request)
  • Have good commit messages
  • Have tests
  • Don't significantly decrease the current code coverage (see coverage/lcov-report/index.html)


To build Handlebars.js you'll need a few things installed.

Before building, you need to make sure that the Git submodule spec/mustache is included (i.e. the directory spec/mustache should not be empty). To include it, if using Git version 1.6.5 or newer, use git clone --recursive rather than git clone. Or, if you already cloned without --recursive, use git submodule update --init.

Project dependencies may be installed via npm install.

To build Handlebars.js from scratch, you'll want to run grunt in the root of the project. That will build Handlebars and output the results to the dist/ folder. To re-run tests, run grunt test or npm test. You can also run our set of benchmarks with grunt bench.

The grunt dev implements watching for tests and allows for in browser testing at http://localhost:9999/spec/.

If you notice any problems, please report them to the GitHub issue tracker at

Running Tests

To run tests locally, first install all dependencies.

npm install

Clone the mustache specs into the spec/mustache folder.

cd spec
rm -r mustache
git clone mustache

From the root directory, run the tests.

npm test

Ember testing

The current ember distribution should be tested as part of the handlebars release process. This requires building the handlebars-source gem locally and then executing the ember test script.

npm link
grunt build release
cp dist/*.js $emberRepoDir/bower_components/handlebars/

cd $emberRepoDir
npm link handlebars
npm test


Handlebars utilizes the release yeoman generator to perform most release tasks.

A full release may be completed with the following:

yo release
npm publish
yo release:publish components handlebars.js dist/components/

cd dist/components/
gem build handlebars-source.gemspec
gem push handlebars-source-*.gem

After this point the handlebars site needs to be updated to point to the new version numbers. The jsfiddle link should be updated to point to the most recent distribution for all instances in our documentation.