---
title: Configuration
description: Add and configure a Flagship binding in your Wrangler configuration file to evaluate feature flags in a Worker.
image: https://developers.cloudflare.com/dev-products-preview.png
---

> Documentation Index  
> Fetch the complete documentation index at: https://developers.cloudflare.com/flagship/llms.txt  
> Use this file to discover all available pages before exploring further. 

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# Configuration

To use Flagship in a Cloudflare Worker, add a Flagship binding to your Wrangler configuration file. The binding gives your Worker access to `env.FLAGS`, which provides methods to evaluate feature flags.

## Add the binding

Add the `flagship` block to your Wrangler configuration file with a binding name and your app ID.

* [  wrangler.jsonc ](#tab-panel-8884)
* [  wrangler.toml ](#tab-panel-8885)

JSONC

```
{  "flagship": [    {      "binding": "FLAGS",      "app_id": "<APP_ID>",    },  ],}
```

TOML

```
[[flagship]]binding = "FLAGS"app_id = "<APP_ID>"
```

Replace `<APP_ID>` with the app ID from your Flagship app. If you have not created an app yet, refer to the [Get started guide](https://developers.cloudflare.com/flagship/get-started/#create-an-app-and-a-flag). The `binding` field sets the name you use to access Flagship in your Worker code (for example, `env.FLAGS`).

## Bind to multiple apps

A single Worker can bind to multiple Flagship apps. Use the array form to define more than one binding:

* [  wrangler.jsonc ](#tab-panel-8886)
* [  wrangler.toml ](#tab-panel-8887)

JSONC

```
{  "flagship": [    {      "binding": "FLAGS",      "app_id": "<APP_ID_1>",    },    {      "binding": "EXPERIMENT_FLAGS",      "app_id": "<APP_ID_2>",    },  ],}
```

TOML

```
[[flagship]]binding = "FLAGS"app_id = "<APP_ID_1>"
[[flagship]]binding = "EXPERIMENT_FLAGS"app_id = "<APP_ID_2>"
```

Each binding is available as a separate property on the `env` object (for example, `env.FLAGS` and `env.EXPERIMENT_FLAGS`).

## Generate types

After adding the binding, run `npx wrangler types` to generate TypeScript types. This creates the `Env` interface with each binding typed as `Flagship`.

TypeScript

```
interface Env {  FLAGS: Flagship;  EXPERIMENT_FLAGS: Flagship;}
```

## Use the binding

Call evaluation methods on `env.FLAGS` to resolve flag values at runtime. Each method accepts a flag key, a default value, and an optional evaluation context.

* [  JavaScript ](#tab-panel-8888)
* [  TypeScript ](#tab-panel-8889)

JavaScript

```
export default {  async fetch(request, env) {    const isEnabled = await env.FLAGS.getBooleanValue("my-feature", false, {      userId: "user-42",    });
    return new Response(isEnabled ? "Feature is on" : "Feature is off");  },};
```

TypeScript

```
export default {  async fetch(request: Request, env: Env): Promise<Response> {    const isEnabled = await env.FLAGS.getBooleanValue("my-feature", false, {      userId: "user-42",    });
    return new Response(isEnabled ? "Feature is on" : "Feature is off");  },};
```

Refer to the [binding API reference](https://developers.cloudflare.com/flagship/binding/) for the full list of methods.

## Local development

Flagship bindings work with `wrangler dev`. Local Workers use the live Flagship app configured by `app_id`. There is no local flag store. Make sure your local Wrangler configuration points to a valid Flagship app before testing evaluations.

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