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

# Snippet API Overview

> The window.zenstep JavaScript API — reference for all methods exposed by the Zenstep snippet.

## The `window.zenstep` object

After the Zenstep snippet loads, it exposes a global `window.zenstep` API. The snippet initialises synchronously by installing a pre-init queue, so you can call any method before the script has fully loaded — calls are queued and replayed on init.

```typescript theme={null}
interface ZenstepAPI {
  identify: (userId: string, attributes?: UserAttributes) => void;
  track: (event: string, data?: Record<string, unknown>) => void;
  _q: Array<["identify" | "track", unknown[]]>;
}

interface UserAttributes {
  [key: string]: string | number | boolean | undefined;
}
```

***

## Queue behaviour

The snippet uses the GA4 dataLayer pattern. Before the snippet bundle has evaluated, `window.zenstep` is a stub that captures calls:

```javascript theme={null}
// This is safe to call at any point in your page lifecycle
window.zenstep?.identify("user_123");
window.zenstep?.track("onboarding_started");
```

When the bundle evaluates, it drains the queue in order — your calls are not lost.

***

## Methods

| Method                                | Description                                                                    |
| ------------------------------------- | ------------------------------------------------------------------------------ |
| [`identify()`](/snippet-api/identify) | Associate the current browser session with a known user ID and optional traits |
| [`track()`](/snippet-api/track)       | Send a custom behavioural event for use in targeting rules                     |

***

## Calling conventions

All methods are fire-and-forget — they do not return a Promise. Errors are caught internally and logged as warnings to the browser console. Your code will never throw due to a Zenstep API call.

```javascript theme={null}
// No await needed
window.zenstep?.identify("user_123", { plan: "grow" });

// Optional chaining (?.) prevents errors if snippet fails to load
window.zenstep?.track("feature_used", { feature: "csv_export" });
```

***

## Identity state

Zenstep persists identity state in `localStorage` under the key `zenstep_identity`. The identity survives page reloads but is cleared when the user clears their browser data or you call `identify()` with a new user ID.

An **anonymous ID** (`zenstep_anonymous_id`) is created on first load and persists across page reloads before `identify()` is called. This allows Zenstep to track behaviour and show flows to unauthenticated users.