Skip to content


Repository files navigation


CI Coverage Status npm version

Preload function environment variables into Serverless. Use this plugin if you have variables stored in a .env file that you want loaded into your functions.

This used to also preload environment variables into your serverless.yml config, but no longer does with serverless>=2.26.0. See this discussion thread or the FAQ below for details on the impact of how environment variables are loaded with serverless>=2.26.0 and serverless>=3.0.0.**

Do you need this plugin?

Serverless Framework can now natively resolve ${env:xxx} variables from .env files by setting useDotenv: true in the configuration:

useDotenv: true

    FOO: ${env:FOO}

For more complex situations, you will need to wire up dotenv yourself.

This plugin is only useful if you want to automatically import all variables from .env into functions:

  - serverless-dotenv-plugin

    # With the plugin enabled, all variables in .env are automatically imported

Install and Setup

First, install the plugin:

> npm i -D serverless-dotenv-plugin

Next, add the plugin to your serverless config file:

service: myService
  - serverless-dotenv-plugin

Now, just like you would using dotenv in any other JS application, create your .env file in the root of your app:


When deploying, all the variables listed in .env will automatically be available in the deployed functions.

Automatic ENV File Resolution

By default, the plugin looks for the file: .env. In most use cases this is all that is needed. However, there are times where you want different env files based on environment. For instance:


When you deploy with NODE_ENV set: NODE_ENV=production sls deploy the plugin will look for files named .env, .env.production, .env.production.local. If for some reason you can't set NODE_ENV, you could always just pass it in as an option: sls deploy --env production or sls deploy --stage production. If NODE_ENV, --env or --stage is not set, it will default to development.

DEPRECATION WARNING: as of serverless>=3.0.0, --env will not be supported due to changes to the Serverless Framework. See FAQ for details.

The precedence between the options is the following: NODE_ENV > --env > --stage

The env resolution pattern follows the one used by Rail's dotenv and create-react-app

Valid .env file names Description
.env Default file, always included
.env.local Included in all environments except test
.env.development If NODE_ENV or --env or --stage is not set, will try to load .env.development.
.env.{ENV} If NODE_ENV or --env or --stage is set, will try to load .env.{env}.
.env.{ENV}.local Every env set up in .env.{ENV}.local will override other envs

Note: .env, .env.development, and .env.production files should be included in your repository as they define defaults. .env*.local should be added to .gitignore, as those files are intended to be ignored. .env.local is where secrets can be stored.

Lambda Environment Variables

Again, remember that when you deploy your service, the plugin will inject these environment vars into every lambda functions you have and will therefore allow you to reference them as process.env.AUTH0_CLIENT_ID (Nodejs example). If this behaviour is not desireable, set include to [].

Plugin options

All options are optional.

    # default: project root
    path: path/to/my/dotenvfiles

    # if set, ignores `path` option, and only uses the dotenv file at this location
    # basePath: path/to/my/.env

    # if set, uses provided dotenv parser function instead of built-in function
    dotenvParser: dotenv.config.js

    # default: adds all env variables found in your dotenv file(s)
    # this option must be set to `[]` if `provider.environment` is not a literal string
      - DDB_TABLE
      - S3_BUCKET

    # default: does not exclude any env variables found in your dotenv file(s)
    # does nothing if `include` is set
      - NODE_ENV              # Can not be declared for Google Cloud Functions

    # defaults to `true`
    logging: false

    # default: plugin does not cause an error if any file or env variable is missing
      # default: []
        - API_KEY

      # default: false
      file: true

    # default: true
    variableExpansion: false
  • path (string)

    • The plugin will look for your .env file in the same folder where you run the command using the file resolution rules as described above, but these rules can be overridden by setting the path option.
    • This will disable automatic env file resolution.
  • basePath (string)

    • The problem with setting the path option is that you lose environment resolution on the file names.
    • If you don't need environment resolution, the path option is just fine.
  • dotenvParser (string)

    • Path to a custom dotenv parser, relative to the project root (same level as serverless.yml).
    • Parameters passed into the function: { dotenv, paths }.
      • dotenv: dotenv library provided for you or you can bring your own
      • paths: all the dotenv files discovered by the plugin, ordered by precedence (see Automatic ENV File Resolution above for details)
    • This function must return a single object, where each key/value pair represents the env var name and value.
    • By default, this uses the built-in parser, which calls dotenv followed by dotenv-expand for each file.
  • include (list or '*') (default: '*')

    • All env vars found in your file will be injected into your lambda functions.
    • If you do not want all of them to be injected into your lambda functions, you can specify the ones you want with the include option.
    • If set to '*', all env vars in all dotenv files will be injected.
    • If set to an empty list ([]), no env vars will be injected.
    • This option must be set to [] if provider.environment is not a literal string (see FAQ for details).
  • exclude (list)

    • If you do not want all of them to be injected into your lambda functions, you can specify the ones you do not want with the exclude option.
    • Note, this is only available if the include option has not been set.
  • logging: true|false

    • Supresses all logging done by this plugin if no errors are encountered.
  • required

    • env: (list)
      • A set of env var that must be set either in the Serverless environment or via a dotenv file.
      • Throws an error if a required env var is not found.
      • By default, no env vars are required.
    • file: true|false (default false)
      • By default, this plugin will exit gracefully and allow Serverless to continue even if it couldn't find a .env file to use.
      • Set this to true to cause Serverless to halt if it could not find a .env file to use.
  • v4BreakingChanges: true|false (default false)

    • Set this to true to introduce v3.x.x => v4.x.x breaking changes now
  • variableExpansion: true|false (default true)

    • By default, variables can reference other variables
      • E.g. INNER_ENV=innerenv, OUTER_ENV=hi-$INNER_ENV, would resolve to INNER_ENV=innerenv, OUTER_ENV=hi-innerenv
    • Setting this to false will disable this feature
      • E.g. INNER_ENV=innerenv, OUTER_ENV=hi-$INNER_ENV, would resolve to INNER_ENV=innerenv, OUTER_ENV=hi-$INNER_ENV

Example dotenvParser file:

// You can bring your own or use the one provided by the plugin
const dotenv = require('dotenv')
const dotenvExpand = require('dotenv-expand')

module.exports = function({ dotenv, paths }) {
  const envVarsArray = [...paths]
    .map(path => {
      const parsed = dotenv.config({ path })
      return dotenvExpand(parsed).parsed

  return envVarsArray.reduce((acc, curr) => ({ ...acc, ...curr }), {})


You can find example usage in the examples folder.


The changelog is available in the file in the package or on GitHub.


This plugin loads the dotenv environment variables inside the plugin constructor. Aside from legacy reasons, this also means all your dotenv environment variables are available to the other plugins being loaded.

However, Serverless variables are not resolved in the constructor:

Variable references in the serverless instance are not resolved before a Plugin's constructor is called, so if you need these, make sure to wait to access those from your hooks. ~

This is important for several FAQ items below.

How has changes to the Serverless Framework affected when environment variables are loaded?


serverless/serverless#8987 changed the order of when plugins are initialized in relationship to variable resolution as part of a larger initiative outlined in serverless/serverless#8364. Because of this, any env var references inside JavaScript files will now get evaluated too early in the process.


env variables will get resolved before this plugin is initialized. This means env variables inside serverless.yml can no longer rely on this plugin to load them from dotenv files. See serverless/serverless#8364 for more details on the changes made to the Serverless Framework variables engine.

The Serverless Framework has basic dotenv support built-in. For support with more complicated workflows with dotenv, see serverless-dotenv-example for details.

You can continue to use this plugin to automatically load environment variables into all your functions using dotenv.

How has changes to the Serverless Framework affected configuration options?

See deprecation code UNSUPPORTED_CLI_OPTIONS for more details. This was introduced in serverless/serverless#9171.


Using the --env CLI option will now result in the following warning:

Detected unrecognized CLI options: "--env".
Starting with the next major, Serverless Framework will report them with a thrown error
More Info:


Using the --env CLI option will now result in the following error:

Detected unrecognized CLI options: "--env".

Why do env vars already defined by the system take higher precedence?

The Serverless Framework has basic dotenv support built-in. If you are loading variables from .env at the project root, it is possible the Serverless Framework preloads that env var before this plugin does.

As well, because of the variables engine changed in serverless>=2.26.0 (see above), env variables can also be resolved before this plugin runs, which means Serverless could take the values already defined in the system before the plugin loads env vars via dotenv.

Why doesn't the basePath or path options support Serverless variables?

Because Serverless variables have not been interpolated when this plugin runs, basePath and path will always be treated like literal strings (e.g. ${opt:stage} would be presented to the plugin, not the passed in via --stage). The suggested pattern is to store all your dotenv files in one folder, and rely on NODE_ENV, --env, or --stage to resolve to the right file.

There are no plans to support anything other than literal strings at this time, although you are free to discuss this in #52.

Why doesn't this plugin work when provider.environment references another file?

Upgrade to serverless>=2.26.0. The new variables engine introduced in the Serverless Framework in v2.26.0 now resolves file variables first before loading initializing any plugins.

Before v2.26.0, Serverless variables do not get interpolated before this plugin gets initialized, causing provider.environment to be presented to this plugin uninterpolated (e.g. ${file(./serverless-env.yml):environment}). Because of this, the plugin tries to append items to a string instead of a list.

To work around this, you can set the include option to [] to avoid adding any environment variables to provider.environment. However, this means you will have to wire up the environment variables yourself by referencing every single one you need. E.g.

    - DDB_TABLE: ${env:DDB_TABLE}

More details are available at #38.


Because of the highly dependent nature of this plugin (i.e. thousands of developers depend on this to deploy their apps to production) I cannot introduce changes that are backwards incompatible. Any feature requests must first consider this as a blocker. If submitting a PR ensure that the change is developer opt-in only meaning it must guarantee that it will not affect existing workflows, it's only available with an opt-in setting. I appreciate your patience on this. Thanks.