Firefox On Windows To Get Faster Startup Times

Martin Brinkmann
Jan 24, 2011
Updated • Mar 1, 2015

When you look at complaints of Firefox users you notice that startup times of the browser are mentioned a lot.

Most users state that Firefox's startup times are slower than those of comparable web browsers on the same system.

And while I'm personally not able to see much of a difference between the startup time of Firefox and other browsers such as Google Chrome on a fast Windows 7 system with Solid State Drive, other users with slower hard drives may very well see bigger differences.

That however appears to be a thing of the past, at least if the proposed patch passes quality control.

Chances are however good that it will be compiled in one of the latest nightly versions of Firefox 4 Beta. Here is what Taras Glek, the developer who proposed the code change, discovered:

We page in most of xul.dll and mozjs.dll. So i figured why not try lazy-linking libxul and preloading it. Turned out lazylinking didnt make any difference, but
preloading seems to consistently shave up 2seconds of startup on my profile(40%).
I'm going to doublecheck on my favourite user's slow computer. Here is the patch in meantime.

Basic idea is that the sequential flag + bullshit read tricks windows into reading xul in 2mb chunks instead of stupid 32k(or smaller) ones. Have to do it this way because there is no fadvise() on Windows(that I know of) A big sequential read cuts down on a lot of seeks.

I just confirmed, this also works wonders on slow harddrives. Shaved around 50% off cold startup on my reference slow system

A loading time reduction of 40-50% with a 20 line patch, that sounds efficient. But how is this achieved? From what I can gather, the developers are now pre-loading files in larger chunks which cuts down on the loading time of the browser especially on slower hard drives.

It will be interesting to test this on computers with slow Firefox startup times. Information about the patch are posted on Bugzilla. (via)

This is not the only startup improvement that Mozilla integrated in Firefox in recent time. The organization added BarTab like on-demand tab loading to Firefox so that only the active tab is loaded which speeds up start during session restore considerably.


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  1. Thomas said on January 24, 2011 at 11:52 am

    Not to forget to remove unused languages/locales from extensions. I do it since I read your recommendation and this speeds up FF startup too. Maybe you add it to the related articles too.

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