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 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 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.