

Link prefetching FAQ - theandrewbailey
https://developer.mozilla.org/en-US/docs/Web/HTTP/Link_prefetching_FAQ

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nfoz
I don't understand how this:

> prefetching is a browser feature; users should be able to disable it easily.

can be preceded so closely by this:

> there is a hidden preference that you can set to disable link prefetching.

> However, the theory is that if link prefetching needs to be disabled then
> there must be something wrong with the implementation.

And later:

> Privacy implications

> Along with the referral and URL-following implications already mentioned
> above, prefetching will generally cause the cookies of the prefetched site
> to be accessed. (For example, if you google amazon, the google results page
> will prefetch www.amazon.com, causing amazon cookies to be sent back and
> forth.

I honestly can't see this feature doing anything more than harm. Every site
has it in their interest to declare every link as pre-fetched, because it will
make that site "seem faster". And this will cost every user a lot of hidden
bandwidth and cache. Am I crazy?

~~~
theandrewbailey
Sites also have an interest in reducing their network usage.

This technique is useful for a multipage process, or some other flow where
there is, say, 50+% chance that the user will go to a specific page. It can be
verified through analytics.

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billyhoffman
I don't get it. This feature appeared years and years ago. The FAQ itself
mentioned "starting with Firefox 3.5" which is from 2009. This isn't new, and
it's not unique to FireFox. Modern IE has something like this as well.

HTTP/2's Server Push implements this concept at the protocol layer.

~~~
theandrewbailey
Support for this is already widespread, so it can be used right now. HTTP/2
support is very low, and I'm not sure if this should be a protocol level
responsibility or not.

~~~
billyhoffman
I completely agree with you about HTTP/2 push. I guess I don't understand why
this prefetching via HTML tags or HTTP headers is getting discussed now on HN
. Its several years old, and there have been no new advances, short of HTTP2,
which is not mentioned in this FAQ. The FAQ itself hasn't been updated in
quite some time

~~~
theandrewbailey
Just because it's old doesn't mean that it's useless, or widely known.

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hashberry
This is great. Can stop hacky prefetching like hidden images or Ajax calls.
Front-end optimization is easily overlooked, yet something that greatly
influences the user's experience on a site.

