Introducing Heroku Fork

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An application is more than source code - it’s executables, generated assets, runtime environments, dependencies, configuration, running processes, backing services and more. What if you could fork your entire app, not just your code?

heroku fork lets you create unique, running instances of existing applications right from the command line. These instances are live and available on Heroku immediately so you can change, scale and share them however you want.

You can fork apps you own and apps you’re collaborating on. You must have the Heroku Toolbelt installed to use this feature. Fork an existing application by running the following command:

$ heroku fork -a sourceapp targetapp

The command:

Copies the source app's precompiled slug. Copies the source app's config vars, excluding add-on-specific environment variables. Re-provisions the source app's add-ons with the same plan. Note that if you are using paid add-ons, you will be charged for their usage in the new app. Copies the source app's Heroku Postgres data, if present. Scales the web process of the new app to one dyno, regardless of the number of web processes running on the source app. This ensures you don’t pay for scale you may not need.

For more on the specific behaviors and limitations of heroku fork , please see the Dev Center article.

The common practice for evaluating pull requests is cumbersome at best: submitters provide a screenshot (or animated gif) to illustrate the proposed change, or a maintainer pulls down the remote branch and previews the change locally. Using heroku fork , pull requests can be accompanied by the URL of a live fork of the app that demonstrates a real, interactive version of the new feature.

Keeping development, staging, production and other environments as similar as possible provides the foundation for a healthy workflow. Using heroku fork you can quickly spin up new, homogeneous application environments for other stages of development. You may even want additional environments outside of the standard development/staging/production workflow - heroku fork provides a simple way to spin up more ephemeral environments to play with, modify or dispose of as desired.

We recently launched Heroku Europe. heroku fork can be used to migrate your application to the Europe region:

$ heroku fork -a sourceapp targetapp --region eu

After verifying add-on provisioning and config vars in the new application, you can take steps to complete migration, such as migrating any production data not stored in Heroku Postgres and adjusting DNS settings.