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Environment variables

Background

You can add environment variables, which are a type of binding, to attach text strings or JSON values to your Worker. Environment variables are available on the env parameter passed to your Worker's fetch event handler.

Text strings and JSON values are not encrypted and are useful for storing application configuration.

Add environment variables via Wrangler

To add env variables using Wrangler, define text and JSON via the [vars] configuration in your Wrangler file. In the following example, API_HOST and API_ACCOUNT_ID are text values and SERVICE_X_DATA is a JSON value.

{
  "name": "my-worker-dev",
  "vars": {
    "API_HOST": "example.com",
    "API_ACCOUNT_ID": "example_user",
    "SERVICE_X_DATA": {
      "URL": "service-x-api.dev.example",
      "MY_ID": 123
    }
  }
}

Refer to the following example on how to access the API_HOST environment variable in your Worker code:

export default {
  async fetch(request, env, ctx) {
    return new Response(`API host: ${env.API_HOST}`);
  },
};

Configuring different environments in Wrangler

Environments in Wrangler let you specify different configurations for the same Worker, including different values for vars in each environment. As vars is a non-inheritable key, they are not inherited by environments and must be specified for each environment.

The example below sets up two environments, staging and production, with different values for API_HOST.

{
  "name": "my-worker-dev",
  "vars": {
    "API_HOST": "api.example.com"
  },
  "env": {
    "staging": {
      "vars": {
        "API_HOST": "staging.example.com"
      }
    },
    "production": {
      "vars": {
        "API_HOST": "production.example.com"
      }
    }
  }
}

To run Wrangler commands in specific environments, you can pass in the --env or -e flag. For example, you can develop the Worker in an environment called staging by running npx wrangler dev --env staging, and deploy it with npx wrangler deploy --env staging.

Learn about environments in Wrangler.

Add environment variables via the dashboard

To add environment variables via the dashboard:

  1. Log in to Cloudflare dashboard ↗ and select your account.
  2. Select Workers & Pages.
  3. In Overview, select your Worker.
  4. Select Settings.
  5. Under Variables and Secrets, select Add.
  6. Select a Type, input a Variable name, and input its Value. This variable will be made available to your Worker.
  7. (Optional) To add multiple environment variables, select Add variable.
  8. Select Deploy to implement your changes.

Compare secrets and environment variables

Secrets are environment variables. The difference is secret values are not visible within Wrangler or Cloudflare dashboard after you define them. This means that sensitive data, including passwords or API tokens, should always be encrypted to prevent data leaks. To your Worker, there is no difference between an environment variable and a secret. The secret's value is passed through as defined.

Local development with secrets

Put secrets for use in local development in either a .dev.vars file or a .env file, in the root of your project.

Choose to use either .dev.vars or .env but not both. If you define a .dev.vars file, then values in .env files will not be included in the env object during local development.

These files should be formatted using the dotenv ↗ syntax. For example:

.dev.vars / .env
SECRET_KEY="value"
API_TOKEN="eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"

To set different secrets for each Cloudflare environment, create files named .dev.vars.<environment-name> or .env.<environment-name>.

When you select a Cloudflare environment in your local development, the corresponding environment-specific file will be loaded ahead of the generic .dev.vars (or .env) file.

  • When using .dev.vars.<environment-name> files, all secrets must be defined per environment. If .dev.vars.<environment-name> exists then only this will be loaded; the .dev.vars file will not be loaded.
  • In contrast, all matching .env files are loaded and the values are merged. For each variable, the value from the most specific file is used, with the following precedence:
    • .env.<environment-name>.local (most specific)
    • .env.local
    • .env.<environment-name>
    • .env (least specific)