---
title: Environment variables in Compose
description: How to set, use and manage environment variables in Compose
keywords: compose, orchestration, environment, env file
redirect_from:
- /compose/env/
- /compose/link-env-deprecated/
---

There are multiple parts of Compose that deal with environment variables in one
sense or another. This page should help you find the information you need.


## Substitute environment variables in Compose files

It's possible to use environment variables in your shell to populate values
inside a Compose file:

```yaml
web:
  image: "webapp:${TAG}"
```

If you have multiple environment variables, you can substitute them by adding
them to a default environment variable file named `.env` or by providing a
path to your environment variables file using the `--env-file` command line option.

{% include content/compose-var-sub.md %}

### The “.env” file

You can set default values for any environment variables referenced in the
Compose file, or used to configure Compose, in an [environment file](env-file.md)
named `.env`. The `.env` file path is as follows:

  - Starting from `v1.28`, the `.env` file is placed at the base of the project directory.
  - Project directory can be explicitly defined with the `--file` option or `COMPOSE_FILE`
  environment variable. Otherwise, it is the current working directory where the `docker compose` command is executed (`+1.28`).
  - For versions older than `v1.28`, it might have trouble resolving `.env` file with `--file` or `COMPOSE_FILE`. To work around it, it is recommended to use `--project-directory`, which overrides the path for the `.env` file. This inconsistency is addressed in `v1.28` by limiting the file path to the project directory.


```console
$ cat .env
TAG=v1.5

$ cat docker-compose.yml
version: '3'
services:
  web:
    image: "webapp:${TAG}"
```

When you run `docker compose up`, the `web` service defined above uses the
image `webapp:v1.5`. You can verify this with the
[convert command](../engine/reference/commandline/compose_convert.md), which prints your resolved application config to the terminal:

```console
$ docker compose convert

version: '3'
services:
  web:
    image: 'webapp:v1.5'
```

Values in the shell take precedence over those specified in the `.env` file.

If you set `TAG` to a different value in your shell, the substitution in `image`
uses that instead:

```console
$ export TAG=v2.0
$ docker compose convert

version: '3'
services:
  web:
    image: 'webapp:v2.0'
```

You can override the environment file path using a command line argument `--env-file`.

### Using the “--env-file”  option

By passing the file as an argument, you can store it anywhere and name it appropriately, for example, `.env.ci`, `.env.dev`, `.env.prod`. Passing the file path is done using the `--env-file` option:

```console
$ docker compose --env-file ./config/.env.dev up
```

This file path is relative to the current working directory where the Docker Compose
command is executed.

```console
$ cat .env
TAG=v1.5

$ cat ./config/.env.dev
TAG=v1.6


$ cat docker-compose.yml
version: '3'
services:
  web:
    image: "webapp:${TAG}"
```

The `.env` file is loaded by default:

```console
$ docker compose convert
version: '3'
services:
  web:
    image: 'webapp:v1.5'
```

Passing the `--env-file` argument overrides the default file path:

```console
$ docker compose --env-file ./config/.env.dev config
version: '3'
services:
  web:
    image: 'webapp:v1.6'
```

When an invalid file path is being passed as `--env-file` argument, Compose returns an error:

```console
$ docker compose --env-file ./doesnotexist/.env.dev  config
ERROR: Couldn't find env file: /home/user/./doesnotexist/.env.dev
```

For more information, see the
[Variable substitution](compose-file/compose-file-v3.md#variable-substitution) section in the
Compose file reference.


## Set environment variables in containers

You can set environment variables in a service's containers with the
['environment' key](compose-file/compose-file-v3.md#environment), just like with
`docker run -e VARIABLE=VALUE ...`:

```yaml
web:
  environment:
    - DEBUG=1
```

## Pass environment variables to containers

You can pass environment variables from your shell straight through to a
service's containers with the ['environment' key](compose-file/compose-file-v3.md#environment)
by not giving them a value, just like with `docker run -e VARIABLE ...`:

```yaml
web:
  environment:
    - DEBUG
```

The value of the `DEBUG` variable in the container is taken from the value for
the same variable in the shell in which Compose is run.

## The “env_file” configuration option

You can pass multiple environment variables from an external file through to
a service's containers with the ['env_file' option](compose-file/compose-file-v3.md#env_file),
just like with `docker run --env-file=FILE ...`:

```yaml
web:
  env_file:
    - web-variables.env
```

## Set environment variables with 'docker compose run'

Similar to `docker run -e`, you can set environment variables on a one-off
container with `docker compose run -e`:

```console
$ docker compose run -e DEBUG=1 web python console.py
```

You can also pass a variable from the shell by not giving it a value:

```console
$ docker compose run -e DEBUG web python console.py
```

The value of the `DEBUG` variable in the container is taken from the value for
the same variable in the shell in which Compose is run.

>**Note**
>
> When you set the same environment variable in multiple files, there's a precedence rule used by Compose when trying to resolve the value for the variable in question.
You can find this precedence rule and a table illustrating how interpolation works in the [Environment variables precedence](../compose/envvars-precedence.md) page.

In the example below, we set the same environment variable on an Environment
file, and the Compose file:

```console
$ cat ./Docker/api/api.env
NODE_ENV=test

$ cat docker-compose.yml
version: '3'
services:
  api:
    image: 'node:6-alpine'
    env_file:
     - ./Docker/api/api.env
    environment:
     - NODE_ENV=production
```

When you run the container, the environment variable defined in the Compose
file takes precedence.

```console
$ docker compose exec api node

> process.env.NODE_ENV
'production'
```

Having any `ARG` or `ENV` setting in a `Dockerfile` evaluates only if there is
no Docker Compose entry for `environment`, `env_file` or `run --env`.

> Specifics for NodeJS containers
>
> If you have a `package.json` entry for `script:start` like
> `NODE_ENV=test node server.js`, then this overrules any setting in your
> `docker-compose.yml` file.

## Configure Compose using environment variables

Several environment variables are available for you to configure the Docker
Compose command-line behavior. They begin with `COMPOSE_` or `DOCKER_`, and are
documented in [CLI Environment Variables](reference/envvars.md).
