Firefox's Unwanted Prefetched Cookies via Google

Story Text:

Im not certain how to explain this one, but it's weird for sure: Check your cookies and make sure there is nothing there from - then go to google and search for "free slots" (no quotes) - check cookies again and check out the ASP session cookies that have been set...

You can do this by just setting cookies to ask you every time, and denying them if it worries you...

Im using FF, but have no idea what browser the guy that sent this to me (i'll assume he wants to be anon. as he didnt post himself) is using - is it something unique to FF? It looks that way to me, but then im not very familiar with IE and couldnt work out how to test this properly....



-is it because is being prefetched while the SERPs are displaying?

I didn't get that cookie, but then I have disabled prefetch. Simslots seems to be #1 for that search, so it's probably prefetch that does it.

Interesting what you could do if FF supported ActiveX and you had a #1 ranking...

Yup, I am getting the cookie from simslots

I use the Cookie Culler (recommended at TW) on FF.

Zap all unprotected cookies, and simslots cookie is there after doing that G search

Tried the seach with the #2 site "lineslots" and no cookie is set when that comes top for that site

..however Google does, in both cases, set two "PREF" cookies (for .com and which I assume are prefetch

am a little confused

so do you two both have WA

a) installed
b) running

Not WA, only prefetch

It's only prefetch, without WA. Here's the thread


Me, WA?? You must be joking

I must confess to installing it trying it, and uninstalling it, many moons ago!


must've slept through that.

this is a pr nightmare for them if word gets out in general, all those evil cookies appearing everywhere....


Just thought, there is a guy in rural Denmark on dialup right now, who could perhaps use WA :-)

Its the users fault

Lazy surfers should know how to turn off pre-fetching, its their own fault I tell ya.


oh, but the WA is only for broadband, so it won't help Nick while he's on dialup *lol*

In English, please

Can someone explain to a layperson what this is/means?

explain to a layperson


google goes to the first site listed in the serps. and loads it into your browser cache for you, so it's quicker when you click the link :)


Layman's terms

The cookies aren't coming from Google. They are from the first link or two listed in the search results.

Those pages are preloading in your browser's cache -- the temporary internet files.

This type of preloading is referred to as "prefetching" and is a feature of Mozilla and Firefox browsers. Google started taking advantage of it sometime, I believe, in March. If you use firefox or Mozilla as your browser, a site (like Google) can assign a link from the page you visit to be "fetched" and waiting for you in the browser's cache before you visit it.

Another tool that uses prefetching is Google's web accelerator program, which is supposed to speed up how you use the web. It tries to do that by a combination of prefetching, using proxies to load pages faster, and possibly a couple of other strategies.

Regardless of which way a page gets preloaded, if that page serves cookies, it will try to feed you one - even if you don't visit the page.


Thanks bill,

I changed the title a bit, we slap G around a fair bit here, so it seems unfair to bosh 'em when it's not entirely their fault :)

disable it

in FF about:config
look for network.prefetch-next and set to off.

just to round out the thread

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.