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All of the assets used on a StoreFront are offloaded to our cloud CDN partners.  We place all high volume assets as close to the customer on an edge CDN so that the page load times are minimized.

Critical Path CSS

The critical path is the path to rendering a web page.  The browser can not render a page until it has everything necessary for that to happen.  CSS stylesheets block rendering until they are retrieved.  This means the browser has to request, receive, and parse the stylesheet.  Until this is done the page remains blank.  UltraCart will automatically calculate the critical path CSS (all the CSS necessary to render the above the fold content), inject this into the header, and then push all other CSS down to the bottom of the page.  This means the page renders much faster.  Once we know that the customers browser has downloaded the main CSS and cached it, the subsequent requests do not inject critical path CSS.  If the page changes in any way, the critical path CSS is discarded and a new one is calculated in the background.

Lazy Loading of Images

The fastest image on the page is the one that never needs to be loaded.  The Visual Builder's runtime JavaScript libraries will automatically lazy load images once they are visible on the screen or close to scrolling on to the screen.  This leads to a faster perceived page speed for the customer and a reduced amount of bandwidth used by the customer.  This is critical for today's 50% mobile customer environment!

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