Firefox's about:home loading performance improved significantly

Martin Brinkmann
Jul 18, 2020

First impressions count; that is true for everything including web browsers. When it comes to web browsers, startup performance is important. If it takes (a lot) longer than the previously used browser, users may be inclined to go back to the other browser.

Mozilla Firefox loads the about:home page by default. The page resembles the browser's new tab page, but is handled differently by the browser. The web browser displays top sites, highlights (visited sites, recent bookmarks or downloads) and, recommendations by Pocket on the page.

firefox about-home startpage

Firefox users may customize the page, e.g. by pinning sites to the list of top sites, or removing entries from the highlights section.

Most Firefox users that I know enable the browser's "restore previous session" functionality or configure the browser to load one or multiple specific webpages on start.

Those who don't, get about:home any time the browser is started.

Mozilla engineers started to investigate options to improve the loading performance of this essential page.  A new blog post by Mike Conley provides all the details in case you are interested in technical implementation details.

Basically, what Firefox does is cache the about:home page so that it loads faster on consecutive runs. Mozilla's own tests showed a startup performance improvement of about 20%. Conley published a side-by-side video to demonstrate the improvement.

The cache has been integrated into Firefox Nightly already. Nightly users need to enable it at this point in time by loading about:preferences#experimental in the browser's address bar and enabling about:home startup cache on the page that opens. Firefox will cache the page from that moment on to speed up the loading time.

firefox startup cache

Firefox users may clear the cache by loading about:support and selecting the "clear startup cache" option on the page.

Mozilla plans to enable the feature by default in Nightly versions of Firefox soon. Mozilla asks for feedback to eliminate potential bugs before launching the cache for all users of the browser.

The caching is limited to Firefox installations that are configured to load about:home on startup; this means that the following groups of users won't benefit from the cache:

  • Firefox installations that are configured to load the previous browsing session.
  • Firefox installations configured to load different startpages.

There are two additional scenarios in which the cache won't be used. The cache runs on the same browser build only, if the build identifier changes, e.g. after an update of the browser, the cache won't be used on the initial start.

The second exception applies to very fast disks only. If the reading from the disk is faster than the reading from the cache, Firefox will not use the cache.



Firefox's about:home loading performance improved significantly
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Firefox's about:home loading performance improved significantly
Mozilla engineers implemented a caching system for the browser's startpage to improve the loading performance of the web browser on start.
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  1. Haji Sariatullah said on July 20, 2020 at 11:11 pm

    My startpage in Firefox (PC) is “about:blank”
    On Firefox Mobile it’s

  2. Harald said on July 20, 2020 at 12:19 pm

    I am developing websites since the mid 90s. For my development work I am using primarily Chrome and Safari. I like especially the Chrome Inspector. For my personal surfing on Linux and Windows I am using Firefox – and that since the Firebird era :-) This browser never let me down. I could always rely on it, even with 5 windows and 50 tabs open in parallel. Mozilla is one reason why we have today not a by Microsoft controlled browser landscape. The independence of Mozilla encouraged Apple to adopt KHTML (as the open source basis for Safari). And that led finally to Chromium browsers. So without the impact of Firefox and KHTML my daily work would look quite different (less pleasant). I am very grateful for all the outstanding work from these two browser projects (Mozilla and KHTML). I will use Firefox for my personal browsing as long as this is reasonably doable.

  3. ULBoom said on July 20, 2020 at 1:03 am

    First thing I did long ago with about:config was block all that stuff. My home page is a non-google search page; new tab pages are the same with New Tab Homepage extension installed.

    I just move my profile to new versions when they appear.

    If software can spam me without my permission, I can block it without their permission. tee hee

    I don’t understand the obsession with tiny fractions of time loading pages. I guess it gives browser makers something to compare “New, New, New, Look!!!”

  4. ddk said on July 19, 2020 at 10:47 pm

    Props to whoever on here suggested ungoogled chromium, been using for 2 weeks with a few tweaks & adjustments is very responsive without all that other Google crud included.

    When manifest V3 arrives and limitations on filters, will probably have to look for another browser unless chromium devs work around V3 issues.

    Firefox is still too buggy. Slower than chromium and one annoyance that’s a deal breaker is clicking images where either the picture doesn’t load or image is truncated showing only the bottom half, the rest going off the top of the screen. I guess that 3% market share and MS deciding to use a chromium base in Edge says a lot.

    1. Iron Heart said on July 20, 2020 at 1:09 am


      PS: Ungoogled Chromium also exists on Android (F-Droid)…

    2. Iron Heart said on July 20, 2020 at 12:50 am


      Ungoogled Chromium is a genuinely fine and spyware-free browser, I appreciate the project behind it as well. In case you are interested, here is my own setup which I use to improve my online privacy:

      I am using Brave as my main browser, not Ungoogled Chromium, but I still think sections 3) and 4), where I talk about Chromium flags and the extensions I use, could contain valuable info for you.

      Just in case you don’t know how to install extensions in Ungoogled Chromium:

  5. ShintoPlasm said on July 19, 2020 at 2:24 pm

    Not sure what they’re fixing here, as I’ve never experienced any slowdowns on about:home – even using low-tier slow laptops.

  6. Yuliya said on July 19, 2020 at 2:19 pm

    Seriously? Was my comment that offensive?

  7. Tom Hawack said on July 19, 2020 at 10:54 am

    I’ve never been fond of Firefox’s Homepage and NewTab, first because I like neither as they are built, secondly because I prefer the same layout for both. To achieve this(and much more) I have installed the userChromeJS utility from [] and use, for the NewTab itself, the ‘NewTab – Custom Page’ UserChromeJS script from [], even if latest Firefox builds require to replace its ‘aboutNewTabService.newTabURL’ by ‘AboutNewTab.newTabURL’

    Works perfectly :
    UserChromeJS’ ‘NewTab – Custom Page’ allows me to set a Localhost dedicated NewTab ;
    Firefox’s pref(“browser.startup.homepage” is set to same as Localhost dedicated NewTab.

    All of Firefox Homepage related and far more blocked with Ghacks-user.js settings.
    On this clean basis, Firefox opens instantly with my dedicated Homepage, perhaps the only html file I ever built, which displays a home-made Quick/Speed (or whatever you’ll call it) Dial, with no calls to 3rd-partties, 100% local.

    No need for these exotic built-in Home/NewTab pages here. No need and far better suited without them.

  8. lattu said on July 19, 2020 at 8:17 am

    a long time ago i decided to set about:blank as a home page.
    i never regret it

  9. Iron Heart said on July 18, 2020 at 11:48 pm


    From what I hear, Firefox Preview / Nightly still doesn’t have a working about:config, it seems Mozilla doesn’t plan to include one anymore. The Firefox fans in this comment section are in for a nasty surprise, because they won’t be able to fix FF’s awful defaults (Pocket, telemetry, FF experiments, recommendations, bad website-related settings) anymore. Plus, they will be receiving woke messages on their New Tab Page every single day. Their reactions at this renewed Mozilla backstabbing of their user base will be interesting to observe, so much is clear.

    Disclaimer: Of course I do not support Mozilla taking user choice away out of principle, although I am not surprised in the slightest.

    1. Ray said on July 19, 2020 at 5:23 am

      Firefox Nightly (Fenix) does have an about:config.

      1. Iron Heart said on July 19, 2020 at 6:48 am


        Are you sure that you have updated to Fenix already?

        “About:config, unfortunately, probably doesn’t count unless they are going to allow users on the stable release branch to use it, and the talk was (at least as of a few months ago) that they would not be making any about:config functionality available for Fenix users on that channel once it replaces Fenix (Even though the stable version of Firefox, Codename Fennec, currently has it.).”


  10. motang said on July 18, 2020 at 11:05 pm

    That video makes the about:home seem really slow. Mine doesn’t seem like that, then again I don’t have the faster version.

  11. Anonymous said on July 18, 2020 at 9:02 pm

    I really like this move, actually, I loved it. I care about this feature as I don’t own a fast machine.
    BTW, this (fast startup) was the first reason I switched to Firefox a year ago.

    1. ULBoom said on July 20, 2020 at 1:46 am

      Use this if you want to turn FF back into a browser vs. an ad server:

      What’s going on in the background meaning your IPS’s DNS servers, their data mining, your true connection speed, router’s stock firmware’s data mining, etc., can easily make the fastest machine slow.

      Yeah, upgrade but that’s only a part of the story. Fast requires getting the geometric progression of trackers and ads incurred by multi-levels of sharing off your line.

    2. Iron Heart said on July 19, 2020 at 7:44 am


      Upgrading to an SSD (dirt cheap these days) will fix your speed problems, pal.

      1. VioletMoon said on July 19, 2020 at 7:47 pm

        @ IronHeart/Anonymous

        [A] may already have an SSD and the processor is old or the RAM is 4GB. Upgrading to a SSD on an older laptop can be catastrophic if one isn’t careful. The drive is buried beneath the keyboard which has all of the old ribbon interfaces.

        Cloning is easy.

        And new laptops are unbelievable inexpensive at this point.

  12. MartinFan said on July 18, 2020 at 8:59 pm

    I disable everything on homepage except Web Search.

  13. Addy T. said on July 18, 2020 at 7:55 pm

    First impressions do count. Without the deluded “recommendations by Pocket” Firefox would probably have 50%+ of the market share.

    1. ULBoom said on July 20, 2020 at 1:35 am

      Well, almost all that stuff, all recommendations, pocket, reader, ad nauseum can be disabled or cleanly removed.

      I started using FF years before Chrome came out. FF’s market share increased steadily to the mid 30% because people were sick of MS screwing up IE. Here comes Chrome bundled with seemingly every piece of software on the planet, followed soon by Android phones, all of which have Chrome. No one could possibly compete with Google’s global domination of mobile.

      FF was doing a good job catching up with MS, then Google disrupted the browser industry, completely changing the game.

      When IE maxed out mid 50% against FF there was still competition. Google’s monopoly has removed it. Beyond Safari, which has what amounts to a captive market, only bit players remain.

      Mozilla can’t fix that.

    2. Alan Combe said on July 18, 2020 at 9:25 pm

      I doubt that, Mozilla has been hard at work removing most of the customization and freedom from the browser on their mission to make Firefox into a Chrome clone in hopes that will gain relevance and thus market share, but it’s only worked to push people away from the browser. Now it has 3% world market share, in another 5 years it will have below 0.5% world market share and in another 5 years we will be opening FIREFOX.COM from Web Archive.

      1. Iron Heart said on July 19, 2020 at 7:58 am

        @Addy T.

        > Firefox would probably have 50%+ of the market share.

        Even in its heyday, when it was actually about user choice and privacy, Firefox’s market share never exceeded 30%… Why should they now reach 50% all of a sudden, with a wannabe Chrome that displays highly divisive snippet messages on the New Tab Page? Nah, don’t think so.

        I prefer Brave or Ungoogled Chromium over Mozilla’s most recent shenanigans.

  14. Mothy said on July 18, 2020 at 6:13 pm

    This is of no use to me as I’ve been using a blank page (about:blank) for home or new tab for as long as I can remember (on any browser used). I prefer starting with a clean slate then primarily use bookmarks to get where I want to go.

    1. ard said on July 19, 2020 at 3:51 am

      I have made a separate document (HTML) with all my favorite bookmarks, subdivided into categories and saved that on my computer. when starting this doc. loads automatically with all my own favorite bookmarks.

  15. VioletMoon said on July 18, 2020 at 5:45 pm

    Loading the Firefox default page has been an instant for me for months. Maybe because it’s cached? It does bring up Pocket which people say invades one’s privacy to the ultimate.

    However, what I discovered yesterday when working with BlueStacks on Windows 10 for another project is the speed of the Chrome browser. I suppose it would be the same with Firefox.

    Now, how do I account for the unbelievable speed difference when using Android vs. Windows? It was truly remarkable. I was even using Proton VPN on Android.

    Linux is slower than Windows. Hmmm . . . .

  16. Anonymous said on July 18, 2020 at 5:24 pm

    I don’t use the Firefox Start Page. It loads a custom website page.

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