As of today, there’s no Heroku buildpack specifically built for deploying Phoenix and Webpack. Having found no consolidated place to learn how to do it, here’s what I did.

First, make webpack run in your local environment. This link explains it well.

Make sure to comment out /priv/static in your .gitignore file.

If you haven’t, add the following buildpacks to your heroku deploy.

# Set the buildpack for your Heroku app
heroku buildpacks:set https://github.com/gjaldon/phoenix-static-buildpack

# Add this buildpack after the Elixir buildpack
heroku buildpacks:add --index 1 https://github.com/HashNuke/heroku-buildpack-elixir

Add a file called compileto the root folder of your app, and add the call to webpack:

ENV=production node_modules/.bin/webpack

Note that ENV=production is optional and should relate to your webpack configuration.

Voilà.