[MichaelApproved]

I'm wonder if they're cutting out a lot of the rendering that PhantomJS is doing. Not to say that any type of rendering is cheap but I'm guessing they have a limited version of a JS rendering engine that does just enough to index the page.

I bet they'd also skip on all the FB like buttons and other common social media elements that don't impact the content.

[Paul-ish]

This makes sense. Would it be sufficient to just see how the content (eg new <ul> elements or something along those lines) on the page changes when JS is executed, without actually rendering anything?

[cmg]

They're starting to consider page load speed as a factor in rankings, which would lead me to believe that they're letting all the social buttons / trackers / media load.

[anon1mous]

How do you know a page has loaded? A complex page with ads, AJAX, WebSockets may be constantly busy. Most social buttons, ads, etc. are now loaded by callbacks, that usually finish after the page has rendered.

[tracker1]

Most of that data flow, barring user interaction is much more limited compared to the initial load of controls, iframes, images, etc... you can visibly see the drop off..

If you look at the network tab in chrome dev tools, you can see when the dom ready event fires, the window load event, and when it really feels the content was done loading. That final load time is when the data flow lulls out for a bit.