WebKit and Chrome prerendering

[spiralganglion]

This sounded like a potentially useful feature for web developers, to improve perceived loading speed without having to use JS (which may be desirable in some situations). But reading Google's notes on the subject is like a splash of cold water: http://code.google.com/chrome/whitepapers/prerender.html

TL;DR: Only one page may be prerendered at a time per-instance of Chrome (not per-tab).

It would be nice to know if this just limits simultaneous prerendering, or if only one link may be prerendered and it must be clicked on or "evicted" before any more prerendering will occur.

[eridius]

I can't speak definitively, but I doubt the prerendered page needs to be visited before another one can be prerendered. If that were the case, I could open a google search and leave it in a background tab and never ever get prerendering ever again.

[r00fus]

Somewhat concerning: "What looks like a real pageview from a modern browser might be a browser downloading your page resources in the background before possibly being presented to an actual visitor. Websites that care about separating eyeballs from machines should add new JavaScript to their pages to create awareness of the current loading state."

So won't this be confusing, as non-discriminating sites choose to inflate their page views by ignoring whether those were prefetches or real loads?

And what about ads?

[mrkurt]

Nearly everything that has to do with ads (both tracking and serving) is already standardized client side script, so it won't make much difference for publishers/advertisers. Ad agencies already want data vetted by someone like Comscore, and most publishers use tools like Google Analytics for their own purposes. I suspect those tools already account for invisible pre-rendering.

This doesn't really effect much, to be honest. People who want to inflate their stats already do so by counting bot traffic, iframe requests, etc. Google's been doing partial javascript evaluation for a long time as part of their spidering.

[petercooper]

So won't this be confusing, as non-discriminating sites choose to inflate their page views by ignoring whether those were prefetches or real loads?

There are a lot of sites out there that use JavaScript reloads every X minutes to do this sort of thing already. More trackable but I bet they still include those numbers in their media packs ;-)

TechCrunch, for example, has this near the bottom of the source:

    setTimeout('location.reload(true)',1200000);

So that's every 20 minutes.

A more insidious trick to "inflate" your views would be to detect when a tab isn't open but still showing your site and to refresh a lot more often in that case (meaning the user won't notice).

[invig]

Security implications? Now your browser will execute JavaScript from sites you didn't even visit. Awesome.

[lovskogen]

Are you sure it doesn't just download?

[pak]

Isn't this Google Web Accelerator, all over again, with the same problems?

http://en.wikipedia.org/wiki/Google_Web_Accelerator

[sjwright]

That's great. Now, how can I opt-out my web server from this?

[jannes]

You can't. Which is great for users.

Think of it like an iframe. Any page can already trigger pageloads of your page that the user might not had intended.

[teraflop]

You don't, just like you don't get to opt out of being the target of a 302 redirect or hidden iframe. But just like both of those, you can detect it and use that information as you see fit.