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git push heroku, Heroku’s slug compiler prepares your code for execution by the Heroku dyno manager. At the heart of the slug compiler is a collection of scripts called a buildpack.
Heroku’s Cedar stack has no native language or framework support; Ruby, Python, Java, Clojure, Node.js and Scala are all implemented as buildpacks.
If you have questions about the build process on Heroku, consider discussing it in the Build forums.
Heroku maintains a collection of buildpacks that are available by default to all Heroku apps during slug compilation.
These buildpacks are open-source and available on Github. If you have a change that would be useful to all Heroku developers, we encourage you to submit a pull request.
By default, these buildpacks will be searched in order until a match is detected and used to compile your app.
Custom buildpacks can be used to support languages or frameworks that are not convered by Heroku’s default buildpacks. For a list of known third-party buildpacks, see Third-Party Buildpacks.
Using a custom Buildpack
You can specify an exact version of a buildpack by using a git revision in your
You can override the Heroku default buildpacks by specifying a custom buildpack in the
BUILDPACK_URL config var:
$ heroku config:set BUILDPACK_URL=https://github.com/heroku/heroku-buildpack-ruby
You can also specify a buildpack during app creation:
$ heroku create myapp --buildpack https://github.com/heroku/heroku-buildpack-ruby
Buildpack URLs can point to either git repositories or tarballs. Hosting a buildpack on S3 can be a good way to ensure it’s highly available.
Creating a buildpack
If you’d like to use a language or framework not yet supported on Heroku you can create a custom buildpack. To get started, see the following articles:
- To learn about the structure of a buildpack, see Buildpack API.
You can use the heroku-buildpacks CLI plugin to publish buildpacks to our catalog.