---
title: "Environment variables"
---

:::info Legacy Documentation

You are viewing legacy documentation for Deno Deploy Classic. We recommend
migrating to the new
<a href="/deploy/">Deno Deploy</a> platform.

:::

Environment variables are useful to store values like access tokens of web
services. Each deployment has a set of environment variables defined at the
moment of creation and accessible from the code via the `Deno.env` API. There
are 2 ways to define the environment variables of a deployment:

## Project environment variables

You can define environment variables at the project level. When you create a
deployment, it will get the set of environment variables the project has defined
_at that particular moment_.

For convenience, When you change the environment variables of a project, the
current production deployment is _redeployed_, creating a new production
deployment with the new set of environment variables.

:::note

Deployments are immutable, including their environment variables. Changing the
environment variables of a project does not change the environment variables of
existing deployments.

:::

To add an environment variable to your project, click on the **Settings** button
on the project page and then on **Environment Variables** from the sidebar. Fill
in the key/value fields and click on "Add" to add an environment variable to
your project.

![environment_variable](../docs-images/fauna2.png)

Updating an existing environment variable works the same way. Click on the "Add
Variable" button, enter the same name of the environment variable you wish to
update and enter the new value. Click on the "Save" button to complete the
update.

## Deployment environment variables

When deploying using `deployctl`, you can specify environment variables
[using the `--env` or `--env-file` flags](./deployctl.md#environment-variables),
complementing the environment variables already defined for the project. You can
also pass multiple `--env-file` arguments (e.g.,
`--env-file=.env.one --env-file=.env.two`) to include variables from multiple
files.

:::note

When multiple declarations for the same environment variable exist within a
single `.env` file, the first occurrence is applied. However, if the same
variable is defined across multiple `.env` files (using multiple `--env-file`
arguments), the value from the last file specified takes precedence. This means
that the first occurrence found in the last `.env` file listed will be applied.

:::

These env variables will be specific for the deployment being created.

### Default environment variables

Every deployment has the following environment variables preset, which you can
access from your code.

1. `DENO_REGION`

   It holds the region code of the region in which the deployment is running.
   You can use this variable to serve region-specific content.

   You can refer to the region code from the [regions page](regions).

1. `DENO_DEPLOYMENT_ID`

   It holds the ID of the deployment.