Mozilla released a 64-bit version of Firefox for Windows that took place as part of the Firefox Developer Edition. For Windows, this is the first time that a 64-bit version of Firefox is available in a major distribution channel. Remember that the Firefox Developer Edition has taken over from the Aurora channel.
When we saw this availability, Mozilla had not yet made an announcement about it. This is now the case via the publication of a post on Mozilla Hacks signed by the director of tools for developers at Mozilla and a technological evangelist for Mozilla.
Logically, it is recalled that with a 32-bit browser, the amount of RAM is limited to 4 GB. And if we can think that this is not a handicap for the case of a Web browser unlike software for video encoding for example, Mozilla evokes the case of large web applications and mainly in the field of video games.
These are in fact arguments similar to those of Google during the debut of Google Chrome 64-bit for Windows (which remains an option). This is to take advantage of 64-bit chips and various optimizations so that more function parameters can be passed quickly into the registers (their memory locations).
Similarly, Mozilla underlines the contribution in terms of security in order to be able to exploit the functionalities making more difficult the attacks by buffer overflow based on accesses to known memory addresses. A 64-bit address space improves the efficiency of Address Space Layout Randomization (ASLR) protection.
The question of a possible compatibility problem with plugins is however not raised. But it must be said that third-party plugins are less and less fashionable.
Mozilla does not specify when we can expect Firefox 64 bit final version for Windows. If all goes well, the normal development cycle would mean that it coincides with the release of Firefox 38 in May.