---
title: Binding API
description: Workers access Flagship through a binding that you add to your Wrangler configuration file. The binding field sets the variable name you use in your Worker code.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Binding API

Workers access Flagship through a binding that you add to your Wrangler configuration file. The `binding` field sets the variable name you use in your Worker code.

* [  wrangler.jsonc ](#tab-panel-6845)
* [  wrangler.toml ](#tab-panel-6846)

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). With this configuration, the binding is available as `env.FLAGS`. Refer to [Configuration](https://developers.cloudflare.com/flagship/configuration/) for additional options such as binding to multiple apps.

The binding provides type-safe methods for evaluating feature flags. If an evaluation fails or a flag is not found, the method returns the default value you provide.

* [  JavaScript ](#tab-panel-6847)
* [  TypeScript ](#tab-panel-6848)

JavaScript

```

export default {

  async fetch(request, env) {

    const enabled = await env.FLAGS.getBooleanValue("new-feature", false, {

      userId: "user-42",

    });

    return new Response(enabled ? "Feature on" : "Feature off");

  },

};


```

TypeScript

```

export default {

  async fetch(request: Request, env: Env): Promise<Response> {

    const enabled = await env.FLAGS.getBooleanValue("new-feature", false, {

      userId: "user-42",

    });

    return new Response(enabled ? "Feature on" : "Feature off");

  },

};


```

The binding has the type `Flagship` from the `@cloudflare/workers-types` package.

* [ Types ](https://developers.cloudflare.com/flagship/binding/types/)
* [ Methods ](https://developers.cloudflare.com/flagship/binding/methods/)

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/flagship/","name":"Flagship"}},{"@type":"ListItem","position":3,"item":{"@id":"/flagship/binding/","name":"Binding API"}}]}
```