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Dotenv handling for deno.


Setup a .env file in the root of your project.

# .env
GREETING=hello world

Then import the configuration using the config function.

// app.ts
import { config } from "";


Then run your app.

> deno app.ts
{ GREETING: "hello world" }


  • path?: string: Optional path to .env file. Defaults to ./.env.
  • export?: boolean: Set to true to export all .env variables to the current processes environment. Variables are then accessable via Deno.env.get(<key>). Defaults to false (individual variables can be exported via export keyword, see below).
  • safe?: boolean: Set to true to ensure that all necessary environment variables are defined after reading from .env. It will read .env.example to get the list of needed variables.
  • example?: string: Optional path to .env.example file. Defaults to ./.env.example.
  • allowEmptyValues?: boolean: Set to true to allow required env variables to be empty. Otherwise it will throw an error if any variable is empty. Defaults to false.
  • defaults?: string: Optional path to .env.defaults file which defaults to ./.env.defaults.

Auto loading

load.ts automatically loads the local .env file on import and exports it to the process environment:

# .env
GREETING=hello world
// app.ts
import "";

> deno --allow-env --allow-read app.ts
hello world

Safe Mode

To enable safe mode, create a .env.example file in the root of the project.

# .env.example
export LOG_PATH="provide a value here"

Then import the configuration with safe option set to true.

// app.ts
import { config } from "";

console.log(config({ safe: true }));

If any of the defined variables is not in .env, an error will occur. This method is preferred because it prevents runtime errors in a production application due to improper configuration.

Another way to suply required variables is externally, like so:

GREETING="hello world" deno --allow-env app.ts

Default Values

Default values can be easily added via creating a .env.defaults file and using the same format as an.env file.

# .env.defaults
# Will not be set if GREETING is set in base .env file
GREETING="a secret to everybody"

Exporting Variables

Sometimes it is necessary to have variables available in the actual program environment, which is accessible as Deno.env.

One option is to set the configuration option export to true. In this case, all variables provided in .env (and in .env.defaults, if provided) will be exported.

Another option is to use export keyword in the actual .env file, with the same syntax as in bash:

# .env
export LOG_PATH="/var/log/server.log"

Note: Variables that already exist in the environment are not overridden with the export: true configuration option or with the export VARIABLE="value" syntax

In the example file, you can use export to require that certain variables be exported:

# .env.example
NUM_THREADS="provide the number of threads"
export LOG_PATH="set the path where to save logs"

The example file will make sure that variable LOG_PATH will have been present in the program environment — either coming from .env, or from .env.defaults (if provided) or if it already has been set up in the environment beforehand

Parsing Rules

The parsing engine currently supports the following rules:

  • BASIC=basic becomes {BASIC: 'basic'}
  • empty lines are skipped
  • lines beginning with # are treated as comments
  • empty values become empty strings (EMPTY= becomes {EMPTY: ''})
  • single and double quoted values are escaped (SINGLE_QUOTE='quoted' becomes {SINGLE_QUOTE: "quoted"})
  • new lines are expanded in double quoted values (MULTILINE="new\nline" becomes
  • inner quotes are maintained (think JSON) (JSON={"foo": "bar"} becomes {JSON:"{\"foo\": \"bar\"}")
  • whitespace is removed from both ends of unquoted values (see more on trim) (FOO= some value becomes {FOO: 'some value'})
  • whitespace is preserved on both ends of quoted values (FOO=" some value " becomes {FOO: ' some value '})


Issues and pull requests welcome. Please run make fmt before commiting.


  • Inspired by the node module dotenv.