---
title: "Environment variables"
description: "A guide to working with environment variables in Deno. Learn about Deno.env API, .env file support, CLI configuration, and special environment variables that control Deno's behavior."
oldUrl:
  - /runtime/manual/basics/env_variables/
  - /runtime/reference/cli/env_variables/
---

There are a few ways to use environment variables in Deno:

## Built-in Deno.env method

The Deno runtime offers built-in support for environment variables with
[`Deno.env`](https://docs.deno.com/api/deno/~/Deno.env).

`Deno.env` has getter and setter methods. Here is example usage:

```ts
Deno.env.set("FIREBASE_API_KEY", "examplekey123");
Deno.env.set("FIREBASE_AUTH_DOMAIN", "firebasedomain.com");

console.log(Deno.env.get("FIREBASE_API_KEY")); // examplekey123
console.log(Deno.env.get("FIREBASE_AUTH_DOMAIN")); // firebasedomain.com
console.log(Deno.env.has("FIREBASE_AUTH_DOMAIN")); // true
```

## .env file

Deno also supports `.env` files. You can tell Deno to read environment variables
from `.env` with the `--env-file` flag, for example:

```sh
deno run --env-file main.ts
```

This will read the `.env` file from the current working directory or the first
parent directory that contains one. If you want to load environment variables
from a different file, you can specify that file as a parameter to the flag.

You can pass multiple `--env-file` flags (e.g.,
`deno run --env-file=.env.one --env-file=.env.two --allow-env <script>`) to load
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.

:::

## `@std/dotenv`

The `dotenv` package in the standard library can be used to load environment
variables from `.env`.

Let's say you have an `.env` file that looks like this:

```sh
GREETING="Hello, world."
```

Import the `load` module to auto-import from the `.env` file and into the
process environment.

```ts
import { load } from "jsr:@std/dotenv";

const env = await load({
  // optional: choose a specific path (defaults to ".env")
  envPath: ".env.local",
  // optional: also export to the process environment (so Deno.env can read it)
  export: true,
});

console.log(env.GREETING);
console.log(Deno.env.get("GREETING"));
```

Run this with `deno run --allow-read --allow-env app.ts`.

Further documentation for `.env` handling can be found in the
[@std/dotenv](https://jsr.io/@std/dotenv/doc) documentation.

## Set a variable when running a command

As with other CLI commands, you can set environment variables before running a
command like so:

```shell
MY_VAR="my value" deno run main.ts
```

This can be useful when you want to vary a task based on an environment
variable, and can be helpfully combined with
[`deno task`](/runtime/reference/cli/task/) commands like so:

```jsonc title="deno.json"
{

  ...
  
  "tasks": {
    "build:full": {
      "description": "Build the site with all features",
      "command": "BUILD_TYPE=FULL deno run main.ts"
    },
    "build:light": {
      "description": "Build the site without expensive operations",
      "command": "BUILD_TYPE=LIGHT deno run main.ts"
    }
  }
}
```

:::note Variables with spaces

When setting environment variables that contain space characters in a `.env`
file, ensure you enclose the value in quotes. For example:

```shell
MY_VAR="my value with spaces"
```

:::

## `std/cli`

The Deno Standard Library has a [`std/cli` module](https://jsr.io/@std/cli) for
parsing command line arguments. Please refer to the module for documentation and
examples.

## Special environment variables

The Deno runtime has these special environment variables.

| name                 | description                                                                                                                                                                       |
| -------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| DENO_AUTH_TOKENS     | A semi-colon separated list of bearer tokens and hostnames to use when fetching remote modules from private repositories<br />(e.g. `abcde12345@deno.land;54321edcba@github.com`) |
| DENO_TLS_CA_STORE    | Comma-separated list of order dependent certificate stores.<br />Possible values: `system`, `mozilla`. Defaults to `mozilla`.                                                     |
| DENO_CERT            | Load certificate authority from PEM encoded file                                                                                                                                  |
| DENO_COVERAGE_DIR    | Set the directory for collecting coverage profile data. This option only works for [`deno test` subcommand](/runtime/reference/cli/test/).                                        |
| DENO_DIR             | Set the cache directory                                                                                                                                                           |
| DENO_INSTALL_ROOT    | Set deno install's output directory (defaults to `$HOME/.deno/bin`)                                                                                                               |
| DENO_REPL_HISTORY    | Set REPL history file path History file is disabled when the value is empty <br />(defaults to `$DENO_DIR/deno_history.txt`)                                                      |
| DENO_NO_PACKAGE_JSON | Disables auto-resolution of `package.json`                                                                                                                                        |
| DENO_NO_PROMPT       | Set to disable permission prompts on access<br />(alternative to passing `--no-prompt` on invocation)                                                                             |
| DENO_NO_UPDATE_CHECK | Set to disable checking if a newer Deno version is available                                                                                                                      |
| DENO_V8_FLAGS        | Set V8 command line options                                                                                                                                                       |
| DENO_JOBS            | Number of parallel workers used for the `--parallel` flag with the test subcommand.<br />Defaults to number of available CPUs.                                                    |
| DENO_KV_ACCESS_TOKEN | Personal access token used when connecting to Deno KV databases (for example via `Deno.openKv` or `@deno/kv` with a KV Connect URL).                                              |
| DENO_WEBGPU_TRACE    | Path to a directory to output a [WGPU trace](https://github.com/gfx-rs/wgpu/pull/619) to when using the WebGPU API                                                                |
| DENO_WEBGPU_BACKEND  | Select the backend WebGPU will use, or a comma separated list of backends in order of preference. Possible values are `vulkan`, `dx12`, `metal`, or `opengl`                      |
| HTTP_PROXY           | Proxy address for HTTP requests (module downloads, fetch)                                                                                                                         |
| HTTPS_PROXY          | Proxy address for HTTPS requests (module downloads, fetch)                                                                                                                        |
| NPM_CONFIG_REGISTRY  | URL to use for the npm registry.                                                                                                                                                  |
| NO_COLOR             | Set to disable color                                                                                                                                                              |
| NO_PROXY             | Comma-separated list of hosts which do not use a proxy (module downloads, fetch)                                                                                                  |