## Filter: wpd_ai_cookie_domain

Set the domain used for Alpha Insights cookies (e.g. session and attribution cookies).

### Description

The plugin uses the current request host (from `home_url()`) as the cookie domain by default. This filter lets you override it so cookies are shared across subdomains (e.g. use `example.com` so both `www.example.com` and `shop.example.com` share the same cookie). No leading dot is used (RFC 6265 deprecates the leading dot).

#### Location

File: `includes/classes/WPDAI_Session_Tracking.php`

Method: `WPDAI_Session_Tracking::get_cookie_domain()`

### Parameters

Parameter | Type | Description
--- | --- | ---
$host | string | The host parsed from `home_url()` (e.g. `www.example.com`)

#### Return

Type: string

The cookie domain to use (e.g. `example.com` for subdomain sharing). Empty string to use default behavior.

### Example Usage

#### Share cookies across subdomains

    add_filter( 'wpd_ai_cookie_domain', 'wpd_ai_cookie_domain_root' );
    function wpd_ai_cookie_domain_root( $host ) {
        // Use root domain so www and shop share the same session
        if ( preg_match( '/^([a-z0-9\-]+\.)?([a-z0-9\-]+\.[a-z]+)$/i', $host, $m ) ) {
            return $m[2];
        }
        return $host;
    }

### Related

- wpd_session_timeout_seconds – Session timeout
- wpd_attribution_timeout_seconds – Attribution window