serverless/docs/environment-variables.md

Resolution of environment variables

To automatically load environment variables from .env files (with the help of the dotenv package), set useDotenv: true in serverless.yml:

useDotenv: true

With that option enabled, .env files will also be excluded from the package in order to avoid uploading sensitive data as a part of a package by mistake.

Support for .env files

The framework looks for .env and .env.{stage} files in service directory and then tries to load them using dotenv. If .env.{stage} is found, .env will not be loaded. If stage is not explicitly defined, it defaults to dev.

Variable expansion

It is possible to define environment variables as a combination of existing ones:

BASE_URL=my.api.com
PROTOCOL=https

URL=$PROTOCOL/$BASE_URL

This is supported through dotenv-expand

Differences against serverless-dotenv-plugin

There are a few differences between above functionality and serverless-dotenv-plugin:

• The framework only loads environments variables locally and does not pass them to your function's environment
• The framework loads variables from only one .env file (if stage-specific .env is found, default .env is not loaded)
• The framework does not support .env.local, .env.{stage}.local, and .env.development files in a similar way to the plugin
• The framework does not use NODE_ENV variable and --env flag when determining stage