Waterfox is the Firefox fork that began as a 64-bit Windows build by Alex Kontos. Kontos first released it on March 27, 2011, when Firefox did not yet offer an official 64-bit Windows build for ordinary users.
The project started as a personal compilation intended to take advantage of 64-bit Windows hardware. It later developed into a broader Firefox-based browser emphasizing performance, customization, and privacy. Waterfox subsequently added macOS, Linux, and Android releases, while retaining its identity as an independent project built from Mozilla technology.
A common mix-up is to treat Waterfox as simply a privacy rebrand. Privacy became an important part of its positioning, but its defining origin was the 64-bit build. LibreWolf is the more direct answer to a question about removing telemetry and tightening privacy defaults; Pale Moon is associated with preserving older Firefox technologies and interface characteristics. Waterfox’s history has also included distinct product generations and periods under different ownership, so descriptions can vary by version.