For users running 64-bit Windows operating systems, Mozilla has default to provide a 64-bit version of the Firefox browser. As the 64-bit version can better play Address Space Layout Randomization (ASLR) function can provide users with a higher level of security protection. If consumers have ample memory space, then the 64-bit browser can access more than 2GB of memory (most 32-bit Windows applications can use the memory online), thereby reducing the number of crashes.
Although Linux and Mac OS X were 64-bit versions a few years ago, and Mozilla had previously planned to abandon the project, the team broke the 64-bit version in November 2012. In 2014, Mozilla announced the restart of the 64-bit Firefox program; early 2015, 64-bit version appeared development channel: November 3, 2015, Mozilla released Firefox 42.0 official version of the first 64-bit version.
According to the official description, the current Windows system to obtain 64-bit Firefox in two ways
2. Wait: Migrate existing 64-bit Windows users using 64-bit Firefox in future version updates. If consumers prefer to use the 32-bit version after the migration, consumers can download and return to the 32-bit version via the Firefox platform and language download page .