

WebKit and Chrome prerendering - friism
http://www.niallkennedy.com/blog/2011/06/webkit-and-chrome-prerendering.html

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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.

~~~
spiralganglion
Yes, that's what I'm afraid of. It's not clearly stated if that is or isn't
the case. Their wording is ambiguous. I'd test this myself using the dev build
of Chrome, but I can't install it where I am.

Anyone else?

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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.

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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?

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petercooper
The article outlines a technique to check whether your page was preloaded or
not using JavaScript. So the JavaScript would need to be run in order to make
that check.

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

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

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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.

~~~
sjwright
When some random site throws my pages into an iframe, at least the user _sees_
what I've served, and I at least have some control -- I can break out of it
with Javascript, or I could even serve completely different content.

It's a bit different though when the biggest fucking site on the internet
joins in.

Why should I be forced to expend bandwidth every time Google decides a page on
my server is relevant to a search result? This could double or even triple my
bandwidth costs.

~~~
teraflop
If you're worried about Google being a bad web citizen, they've already said
that they only use prerendering for the tom search result, and only if they
think it has a very high probability of being clicked. (Based on my limited
testing, this only ever seems to happen with navigational searches.) So you'd
be spending that bandwidth anyway, and your users are getting a better
experience out of it.

If you're worried about the technology itself being abused to DDOS people, I
don't see how it enables any attack methods that didn't already exist.

~~~
sjwright
If it is as you say, only the #1 result for searches that have a high
probability of it being clicked, then it's generally fine with me. If they
were blindly pre-loading the first few results, I'd have a problem.

I guess I should give Google more credit, and assume they're not idiots.

