A Great Firefox Tip for Users With Resource Issues

Updated September 25, 2010

Doc Sheldon

A friend in the Dojo pointed something out today that came as a bit of a surprise to me. It probably shouldn’t have, as it has obviously been around quite a while. But in case I’m not the only one around here that missed, it, I’m sharing it here. Many of you are probably already aware of it, but then, many of you are younger than I am, and perhaps even a bit more alert (although I’m pretty sharp, after my nap).

So hush up and respect your elders!

Firefox is set by default to do a great many things. A few of them are readily altered via your menu bar. Others are not so easily changed. Or for that matter, even visible.

One such is the prefetch instruction. This is an instruction embedded in a link, which tells the browser to go ahead and start preloading the target of the link, in anticipation of a need to load it for viewing by the user. Preloading a large file or image can accelerate pageload, hence improving the user experience.

Those embedded instructions are placed on a page by the developer or webmaster,  in this format:

<link rel="prefetch" href="/images/big.jpeg">

Now, I’m all for improving the user experience. In fact, I see that as my responsibility numero uno. I don’t even have a problem with it being a default setting in Firefox, provided we’re made aware of it. Firefox already has the tendency to open a large number of connections, unbeknownst to the user, and those connections not only slow down our browsing, they can also present a security risk.

And I also understand a webmaster wanting to use rel=”prefetch” to keep his bounce rate down. However, as consumers, I think we each have a right to know and control what our system is doing.

I also don’t think my browser should be downloading cookies from websites that I haven’t even visited.

So, if you’re not already on top of this, and you’d like to disable the Firefox prefetch function (this works in Flock, too, by the way), here’s the procedure:

  1. In the Firefox Address Bar type about:config and press Enter.
  2. You’ll be confronted with a screen warning that you may void your warranty by continuing. Assuming you decide to continue…
  3. Find the option that is named network.prefetch-next and double-click on it.
  4. Change the value to false.
  5. Now, the rel=”prefetch” instruction will not be heeded, when encountered.

See? That wasn’t so bad. You spent more time scrolling down to the network lines, than anything else. 😉 After you’ve restarted your browser, you can check your Task Manager and I’m sure you’ll see the improvement.

This should free up a considerable block of resources for you, depending on the nature of your online activities. I estimate it freed up 20-25% for me, but then, I often have ten or twelve tabs open. And personally, I haven’t noted any appreciable increase in loadtime.


  1. Merci beacoup.

    Upwords of 100 tabs are often open over several window on my screen.
    I have problems letting go of those digital morsels of info.

    Maybe that’s why Safari refuses to work for me now, it’s knackered!

  2. I just did this, and I read it the other day and didn’t do it. I remembered to find this and make the change tonight.
    Yes you were right, it took longer to scroll and find it than to actually do it.

  3. 100 tabs is… a LOT, Bulbboy! I thought I was bad! I would imagine that stopping prefetch should help you free up quite a bit, then.
    Thanks for the comment!

  4. Glad you remembered to come back and do it, Doreen. I hope it makes difference for you.
    Thanks for the comment. Don’t be a stranger!

  5. I ran across this tip / fix for memory issues with Firefox that also addresses the prefetch problem.


  6. Thanks for adding that, Jules! There are some valid points there, but I would caution everyone to take careful notes on any changes they implement in the about:config, as conflicts are always a possibility. If things get wacked, you may need to undo the changes. I’d also advise never to make more than one change, without giving FireFox a spin, and being sure everything is still working properly… nothing worse than having a problem, and not having any idea which of the seven or eight changes you made might have caused it.

    Except for not remembering what you changed, of course! 😉

  7. Corporate Photographer says:

    Do you know about a seo plugin for firefox- i heard you can tell if a blog is dofollow or nofollow- Thanks Grant

  8. Hi, Grant-

    The one I like is called Quirk SearchStatus. It’s an unobtrusive little button on your status bar, that offers a wealth of information, including the ability to highlight all nofollowed links. It’s available through Mozilla as an add-on to Firefox, and I believe it can also be found for other browsers.

    Thanks for dropping in!

  9. Eldad Sotnick-Yogev says:

    Cool Tip – thanks Doc! looking forward to seeing the improvement. I also noticed that stumbleupon appears to be doing the same prefetch function. May be helpful to turn that off as well.