TL;DR
The window load event fires when the entire page, including all dependent resources such as stylesheets, scripts, images, and iframes, has finished loading.
What is Window Load Event?
The window load event fires when the entire page, including all dependent resources such as stylesheets, scripts, images, and iframes, has finished loading.
Learn more in our understanding load timing metrics guide, or work with us through our done-for-you speed optimization service.
How Window Load Event is Measured
The event is reported by the Navigation Timing API and visible in browser developer tools.