How-To Geek

Quick Tip: Turn off Prefetching in Firefox

Firefox has a spooky feature called “Prefetching” that downloads pages that it thinks you are going to click on. (note: this is a good excuse for how those pages ended up in your history). It’s also a waste of CPU and bandwidth that slows Firefox down.

To turn off this behavior, type about:config into the address bar, and then type the following into the Filter bar:



Just double-click the item in the list to change it to false.

Lowell Heddings, better known online as the How-To Geek, spends all his free time bringing you fresh geekery on a daily basis. You can follow him on if you'd like.

  • Published 06/8/07

Comments (6)

  1. Peter

    Thanks for the tip but how does one show the “filter bar”

    There is no entry in Firefox Help

  2. Cassidy

    Peter: The filter bar will appear automatically when you type about:config into the address bar. It will show up at the top of the browsing area.

    How-to Geek: Do you have a source to cite for the comment that prefetching slows Firefox down? My understanding is that only links that are explicitly designed to be prefetched ( or ) are going to be accessed via this mechanism. I’m pulling my knowledge from

  3. Qrystal

    I, personally, turn off prefetching because of the prefetched cookies. I have Firefox configured to ask me about whether to allow a cookie or not, and prefetching definitely slows my browsing when I have to choose whether to allow or deny cookies for pages I haven’t yet visited! (This is what usually reminds me to turn it off, when I set up Firefox on a fresh system. That’s why I’m here today, in fact!)

  4. Joe

    I helped a friend switch to firefox recently and had him turn off prefetch since he has satellite internet and he gets “fapped” when he downloads over a set number of megs per day. A quite low number.
    Anyone who is in this situation that also uses StumbleUpon must ensure they disable prefetch in SU as well.

  5. Chris

    I would recommend leaving it turned on for the average web user. Almost every web user visits their favourite sites over and over again and for this reason prefetching is ideal. It does not slow down the browser very much at all, in fact the only time you should notice a difference is when you actually start the browser. I think the slight sacrifice in performance is worth it! Ultimately thats why mozilla added the feature!

    Most options in in Firefox are preconfigured with the most optimised settings for users. it is quite rare that you would need to alter them, unless you are developing or testing web apps.

  6. Ben

    I have installed FF on several peoples computers and prefetching has almost always caused problems. It will completely kill a dial up connection. And it will hog even a stout broadband connection to the point that the other machines are sluggish when the FF machine is browsing a new website. It chews up costly bandwidth on both ends of the connection, server and user side. It has caused all types of problems for people using the machines. prefetching has caused people to end up with unwanted stuff in the shopping cart because it prefected the “buy” button. It will make some websites unusable because it prefetches the link to a page before you can fill in all the blanks.

    I turn of prefetching on all FF installations i do for anyone, as a base rule.
    Prefetching is banned on any network i manage, as an absolute rule.
    If I detect any prefetching behavior on any computer on the network, it’s mac will be banned until they talk to me face to face.

    I don’t know why in the bloody heck the makers of Firefox enabled such a poorly behaved feature by default.

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