Environment variables

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.

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.

{
	"$schema": "./node_modules/wrangler/config-schema.json",
	"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
		}
	}
}

"$schema" = "./node_modules/wrangler/config-schema.json"
name = "my-worker-dev"

[vars]
API_HOST = "example.com"
API_ACCOUNT_ID = "example_user"

  [vars.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}`);
	},
};

export interface Env {
	API_HOST: string;
}

export default {
	async fetch(request, env, ctx): Promise<Response> {
		return new Response(`API host: ${env.API_HOST}`);
	},
} satisfies ExportedHandler<Env>;

from workers import WorkerEntrypoint, Response

class Default(WorkerEntrypoint):
    async def fetch(self, request):
        # Environment variables are accessed via attribute access on self.env
        return Response(f"API host: {self.env.API_HOST}")

You can also import env from cloudflare:workers to access environment variables from anywhere in your code, including outside of request handlers:

import { env } from "cloudflare:workers";

// Access environment variables at the top level
const apiHost = env.API_HOST;

export default {
	async fetch(request) {
		return new Response(`API host: ${apiHost}`);
	},
};

import { env } from "cloudflare:workers";

// Access environment variables at the top level
const apiHost = env.API_HOST;

export default {
	async fetch(request: Request): Promise<Response> {
		return new Response(`API host: ${apiHost}`);
	},
};

This approach is useful when you need to:

• Initialize configuration or API clients at the top level of your Worker.
• Access environment variables from deeply nested functions without passing env through every function call.

For more details, refer to Importing env as a global.

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.

{
	"$schema": "./node_modules/wrangler/config-schema.json",
	"name": "my-worker-dev",
	// top level environment
	"vars": {
		"API_HOST": "api.example.com"
	},
	"env": {
		"staging": {
			"vars": {
				"API_HOST": "staging.example.com"
			}
		},
		"production": {
			"vars": {
				"API_HOST": "production.example.com"
			}
		}
	}
}

"$schema" = "./node_modules/wrangler/config-schema.json"
name = "my-worker-dev"

[vars]
API_HOST = "api.example.com"

[env.staging.vars]
API_HOST = "staging.example.com"

[env.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.

To add environment variables via the dashboard:

1. In the Cloudflare dashboard, go to the Workers & Pages page.

   Go to Workers & Pages ↗

2. In Overview, select your Worker.

3. Select Settings.

4. Under Variables and Secrets, select Add.

5. Select a Type, input a Variable name, and input its Value. This variable will be made available to your Worker.

6. (Optional) To add multiple environment variables, select Add variable.

7. Select Deploy to implement your changes.

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.

Put secrets for use in local development in either a .dev.vars file or a .env file, in the same directory as the Wrangler configuration file.

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

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)

When you enable nodejs_compat and the nodejs_compat_populate_process_env compatibility flag (enabled by default for compatibility dates on or after 2025-04-01), environment variables are available via the global process.env.

The process.env will be populated lazily the first time that process is accessed in the worker.

Text variable values are exposed directly.

JSON variable values that evaluate to string values are exposed as the parsed value.

JSON variable values that do not evaluate to string values are exposed as the raw JSON string.

For example, imagine a Worker with three environment variables, two text values, and one JSON value:

[vars]
FOO =  "abc"
BAR =  "abc"
BAZ = { "a": 123 }

Environment variables can be added using either the wrangler.{json|jsonc|toml} file or via the Cloudflare dashboard UI.

The values of process.env.FOO and process.env.BAR will each be the JavaScript string "abc".

The value of process.env.BAZ will be the JSON-encoded string "{ \"a\": 123 }".

:::note Note also that because secrets are a form of environment variable within the runtime, secrets are also exposed via process.env.

• Migrating environment variables from Service Worker format to ES modules syntax.