Elfsight Age Verification widget is the easiest way to arrange a page load popup that will check the age of your website visitors. The widget will help make your content accessible for full-aged users and hide it from the underaged. You can set the age limit, choose verification format, embed the widget on all or specific pages, and choose the action after access denial. The style is also under your control, with paintable elements and option to upload pictures.

Demo: https://codecanyon.net/item/elfsight-age-verification/24088592