> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hop.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Builds

> When deploying with GitHub, Hop will automatically infer your build environment and initiate a build for each push to git

Using [Nixpacks](https://nixpacks.com) (a better alternative to Buildpacks), Hop can automatically detect
the language of your app, removing the need to write a Dockerfile for most cases. If a Dockerfile is detected, it will just be built using regular [Buildkit](https://docs.docker.com/build/buildkit/).

## Caching

Docker layers are cached to speed up the build process on a per-deployment basis. As of today, we don't bill for build cache although this may change in the future. Each deployment is assigned a quota of 50GB in build cache - usage can be tracked under the `Resources` tab within the deployment.

## Environment Variables

Your deployment's environment variables are injected into each build - any environment variables imported during runtime will
also exist during build time.

## Building locally with the CLI

By default, `hop deploy` spins up a server-side builder instance. To use your local machine's cache and compute power to build & push your image instead, append the `--local` flag.

## Customizing Configless Builds

If you don't want to specify a `Dockerfile` then you can use the following environment variables to customize your build.

<Info>
  You can find more options on the [Nixpacks
  documentation](https://nixpacks.com/docs/configuration/environment)
</Info>

| Variable               | Description                                                                              |
| ---------------------- | ---------------------------------------------------------------------------------------- |
| `NIXPACKS_INSTALL_CMD` | Override the install command                                                             |
| `NIXPACKS_BUILD_CMD`   | Override the build command                                                               |
| `NIXPACKS_START_CMD`   | Override the start command                                                               |
| `NIXPACKS_PKGS`        | Additional [Nix packages](https://search.nixos.org/packages?channel=unstable) to install |
| `NIXPACKS_APT_PKGS`    | Add additional Apt packages to install                                                   |
| `NIXPACKS_LIBS`        | Add additional Nix libraries to make available                                           |
| `NIXPACKS_DEBIAN`      | Enable Debian base image, used for supporting OpenSSL 1.1                                |
|                        |                                                                                          |