---
title: Bake file reference
---

The Bake file is a file for defining workflows that you run using `docker buildx bake`.

## File format

You can define your Bake file in the following file formats:

- HashiCorp Configuration Language (HCL)
- JSON
- YAML (Compose file)

By default, Bake uses the following lookup order to find the configuration file:

1. `compose.yaml`
2. `compose.yml`
3. `docker-compose.yml`
4. `docker-compose.yaml`
5. `docker-bake.json`
6. `docker-bake.hcl`
7. `docker-bake.override.json`
8. `docker-bake.override.hcl`

You can specify the file location explicitly using the `--file` flag:

```console
$ docker buildx bake --file ../docker/bake.hcl --print
```

If you don't specify a file explicitly, Bake searches for the file in the
current working directory. If more than one Bake file is found, all files are
merged into a single definition. Files are merged according to the lookup
order. That means that if your project contains both a `compose.yaml` file and
a `docker-bake.hcl` file, Bake loads the `compose.yaml` file first, and then
the `docker-bake.hcl` file.

If merged files contain duplicate attribute definitions, those definitions are
either merged or overridden by the last occurrence, depending on the attribute.
The following attributes are overridden by the last occurrence:

- `target.cache-to`
- `target.dockerfile-inline`
- `target.dockerfile`
- `target.outputs`
- `target.platforms`
- `target.pull`
- `target.tags`
- `target.target`

For example, if `compose.yaml` and `docker-bake.hcl` both define the `tags`
attribute, the `docker-bake.hcl` is used.

```console
$ cat compose.yaml
services:
  webapp:
    build:
      context: .
      tags:
        - bar
$ cat docker-bake.hcl
target "webapp" {
  tags = ["foo"]
}
$ docker buildx bake --print webapp
{
  "group": {
    "default": {
      "targets": [
        "webapp"
      ]
    }
  },
  "target": {
    "webapp": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "tags": [
        "foo"
      ]
    }
  }
}
```

All other attributes are merged. For example, if `compose.yaml` and
`docker-bake.hcl` both define unique entries for the `labels` attribute, all
entries are included. Duplicate entries for the same label are overridden.

```console
$ cat compose.yaml
services:
  webapp:
    build:
      context: .
      labels: 
        com.example.foo: "foo"
        com.example.name: "Alice"
$ cat docker-bake.hcl
target "webapp" {
  labels = {
    "com.example.bar" = "bar"
    "com.example.name" = "Bob"
  }
}
$ docker buildx bake --print webapp
{
  "group": {
    "default": {
      "targets": [
        "webapp"
      ]
    }
  },
  "target": {
    "webapp": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "labels": {
        "com.example.foo": "foo",
        "com.example.bar": "bar",
        "com.example.name": "Bob"
      }
    }
  }
}
```

## Syntax

The Bake file supports the following property types:

- `target`: build targets
- `group`: collections of build targets
- `variable`: build arguments and variables
- `function`: custom Bake functions

You define properties as hierarchical blocks in the Bake file.
You can assign one or more attributes to a property.

The following snippet shows a JSON representation of a simple Bake file.
This Bake file defines three properties: a variable, a group, and a target.

```json
{
  "variable": {
    "TAG": {
      "default": "latest"
    }
  },
  "group": {
    "default": {
      "targets": ["webapp"]
    }
  },
  "target": {
    "webapp": {
      "dockerfile": "Dockerfile",
      "tags": ["docker.io/username/webapp:${TAG}"]
    }
  }
}
```

In the JSON representation of a Bake file, properties are objects,
and attributes are values assigned to those objects.

The following example shows the same Bake file in the HCL format:

```hcl
variable "TAG" {
  default = "latest"
}

group "default" {
  targets = ["webapp"]
}

target "webapp" {
  dockerfile = "Dockerfile"
  tags = ["docker.io/username/webapp:${TAG}"]