The waitUntil parameter accepts the following values: domcontentloaded, networkidle0, networkidle2, and load:
domcontentloaded waits for the DOMContentLoaded event to fire, which occurs when the initial HTML document has been completely loaded and parsed.
networkidle0 waits until there are no more than 0 network connections for at least 500 ms.
networkidle2 waits until there are no more than 2 network connections for at least 500 ms. (default)
load waits for the window.load event to fire, which occurs when all page resources (including images, stylesheets, and scripts) have finished loading.