Scheduled for release on January 1, 2013, Firefox 18 will bring a startup performance that is improved by 20 - 25 percent, according to Glek. In a blog post, he noted that half of the speedup was achieved by accelerated library loading.
It appears that Firefox 18 and 19 will deliver in comparison to Firefox 17, which will be released on November 20, more performance improvements. Glek referred to a streamlined tab strip in which the amount of tab closing animations taking more than 400 ms was reduced from a share of about 20 percent to just 3 percent. The overwhelming share of tab animation closings now has a time of about 150 ms.