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

# Lead Tracking

> Convert clicks into leads by signing up visitors with a unique identifier

## Overview

When a visitor comes through an affiliate link, you can convert their click into a lead by calling the signup function. Before signing up, you should check if:

1. The visitor came through an affiliate link (`window.tolt_data` exists)
2. The visitor hasn't already been signed up (`customer_id` is null)

### Example Implementation

```javascript theme={"system"}
async function signUpVisitor(identifier) {
  // Check if visitor came through affiliate link
  if (!window.tolt_data) {
    console.log("Not an affiliate click");
    return;
  }

  // Check if visitor is already signed up
  if (window.tolt_data.customer_id) {
    console.log("Visitor already signed up");
    return;
  }

  try {
    const result = await window.tolt.signup(identifier);
    console.log("Signup successful:", result);
    return result;
  } catch (error) {
    console.error("Signup failed:", error);
  }
}
```

The `identifier` parameter should be unique to each customer (like an email or user ID).

On success, the function returns:

```javascript theme={"system"}
{
  click_id: "30aa8b8d-b846-4827-bd6f-6beb16466841",
  customer_id: "cus_aE1xbsSk3HuZk58B2usFXNSv",
  customer_identifier: "unique_identifier",
  partner_id: "f468da94-f786-485c-9314-3008ce472188",
  program_id: "prg_YRsbPDAKhWAdqJbFACheh",
  message: "Success"
}
```

If the identifier already exists in the system, the function will throw a 409 error:

```javascript theme={"system"}
{
  message: "Customer already exists";
}
```

After a successful signup, `window.tolt_data` will be automatically updated with the new `customer_id`.