BitPay allows you to embed the invoice on your website, so the shopper never has to leave your site during the checkout process.
When you create an invoice with a POST request to BitPay, BitPay returns the "url" field, which is the URL at which this invoice can be viewed.
To display the embedded invoice on your page, append the code &view=iframe to the invoice URL and display this URL as the source in an iframe.
The embedded invoice will automatically update when payments have been received. In addition to the server IPN sent to your notificationURL, the iframe will send a POST message to the parent window that the status has changed.
If your website has a dark background theme, append the code &theme=dark to the invoice URL. Note that the iframe background color is transparent.