Environment variables

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

Built-in Deno.env Jump to heading#

The Deno runtime offers built-in support for environment variables with Deno.env.

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

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 Jump to heading#

Deno supports .env files. You can cause Deno to read environment variables from .env using the --env-file flag: deno run --env-file <script>. This will read .env by default; if you want or need to load environment variables from a different file, you can specify that file as a parameter to the flag. Additionally, 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.

Alternately, the dotenv package in the standard library will load environment variables from .env as well.

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

GREETING="Hello, world."

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

import "jsr:@std/dotenv/load";

console.log(Deno.env.get("GREETING")); // "Hello, world."

Further documentation for .env handling can be found in the @std/dotenv documentation.

std/cli Jump to heading#

The Deno Standard Library has a std/cli module for parsing command line arguments. Please refer to the module for documentation and examples.

Special environment variables Jump to heading#

The Deno runtime has these special environment variables.