Mozilla Firefox is an open-source web browser, so anyone can take its source code and modify it. Various projects have taken Firefox and released their own versions, either to optimize it, add new features, or align it with their philosophy.
These projects all have to release the source code to their browsers and can’t call them Firefox or use official Mozilla branding, such as the Firefox logo.
Mozilla doesn’t provide official builds of Firefox compiled for 64-bit systems yet. Waterfox takes Firefox’s code and compiles it for 64-bit Windows, without adding additional features or making other changes. Many plugins, including Adobe Flash, now have 64-bit versions, so using a 64-bit browser for day-to-day browsing is very possible. If you’ve already got Flash installed, you may need to download its installer to get the 64-bit version, too. The current installers come with both 32 and 64-bit plugins.
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