Starting with Firefox 55, scheduled for an August 8th, 2017 release, unloaded tab handling in the Firefox web browser got a whole lot better.
This should have a positive impact on all Firefox users who restore the last browsing session on start of the browser. It improves the time it takes to load the browser and also the memory consumption.
To hammer home the point, Mozilla employee Dietrich Ayala ran a test with a Firefox profile with 1691 open tabs in the browsing session.
Note: Startup time depends on a number of factors. All Firefox users who load the previous browsing tab on start should see an improvement in startup time and memory use. As a rule of thumb, the more tabs get loaded, the better the improvement.
He tested startup time and memory performance of Firefox 20, 30, 40, and 50 to 56 using that profile. He could not test the profile in Firefox 10 as it would hang and not load the profile at all.
His main findings are that startup time increased significantly from Firefox 20 to Firefox 51, decreased in Firefox 52 to 54, and then fell sharply to the lowest ever value in Firefox 55.
The startup time was at its highest in Firefox 51 which took more than 7 minutes to start the browser. Firefox 52 took more than 5 minutes to start up loading the profile, and Firefox 55 only 15 seconds.
For memory usage, the findings where equally impressive. Memory usage increased up until Firefox 54, and fell sharply in Firefox 55.
Firefox 50 to 54 used about 2 Gigabytes of RAM when loading the profile. The memory usage dropped to less than 0.5 Gigabytes in Firefox 55.
Remember that this is for tabs that are not fully loaded (read inactive). Firefox won't load all websites in all tabs by default on session restore. This is different from Google Chrome which loads all tabs on session restore. Chrome users will notice that the browser will be largely unresponsive during that time.
Chrome does not ship with a native option to load tabs on activation during start. Chrome users may use an extension like Native Lazy Tabs for Chrome to enable this functionality.
The improvements are certainly impressive but that many tabs are an edge case. Still, it highlights that Firefox's startup got a whole lot better in terms of memory use and startup time when the last browsing session is loaded.
I'd like to know what made the startup time and memory use increase by this much in the past. Which changes were made that impacted it negatively?
Now You: What's the startup time of your browser? Do you load all tabs or lazy load tabs?