---
title: Binding API
description: Evaluate Flagship feature flags directly in Cloudflare Workers using the native binding with type-safe methods and automatic fallback.
image: https://edgetunnel-b2h.pages.dev/dev-products-preview.png
---

> Documentation Index  
> Fetch the complete documentation index at: https://edgetunnel-b2h.pages.dev/flagship/llms.txt  
> Use this file to discover all available pages before exploring further. 

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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-9272)
* [  wrangler.toml ](#tab-panel-9273)

**JSONC**

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

**TOML**

```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://edgetunnel-b2h.pages.dev/flagship/get-started/#create-an-app-and-a-flag). With this configuration, the binding is available as `env.FLAGS`. Refer to [Configuration](https://edgetunnel-b2h.pages.dev/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-9274)
* [  TypeScript ](#tab-panel-9275)

**JavaScript**

```js
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**

```ts
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://edgetunnel-b2h.pages.dev/flagship/binding/types/)
* [ Methods ](https://edgetunnel-b2h.pages.dev/flagship/binding/methods/)

```json
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```