The demo will show a graph of page's overall visual progress over time. The data is based on loading progress measured by a ServiceWorker running in the browser. Actual on-screen rendering may be different due to refresh throttling and quality of JPEG decoding implementation.
In the graphs the X axis is time. Y axis is visual completion of the page. Orange represents percentage of images with some preview likely rendered on screen. Green is percentage of images which should look good enough. White is percentage of images that finished loading.
Thanks to prioritization image sizes are loaded very early (dark gray area jumping to 100%), allowing browsers to perform final page layout almost immediately. The slope of the orange area is much steeper, meaning the images are drawn on the screen sooner. Without prioritization page looks 90% done only after loading 90% of data. With prioritization the page looks 90% done (green area reaching 90%) after loading only about 2/3rds of the data. In both cases the total amount of data loaded is the same, but prioritized deliver looks as if images were compressed much better.
The difference between prioritized and non-prioritized traffic is more visible on slow connections (2G/3G). Simulated slow connection speed in Developer Tools does not simulate network speed accurately enough, and may give results that don't represent real-world improvement.
If the graph does not show up, reload the page.