There are several legitimate reasons users seek out older builds:
HTTP/2, WebP images, AV1 video, and newer CSS Grid features will either be slow or invisible.
You will encounter breakage:
The single biggest driver is legacy add-ons. When Mozilla deprecated XUL/XPCOM extensions in favor of WebExtensions (around Firefox 57, codenamed "Quantum"), millions of powerful add-ons became obsolete. Waterfox initially resisted this change. Waterfox browser old version builds (specifically versions 56.x and earlier) retained full support for legacy extensions like:
If you rely on a niche corporate intranet tool or a deeply customized add-on built before 2017, the only way to keep using it is with an older Waterfox version. waterfox browser old version
While Waterfox is privacy-focused, older versions are completely devoid of any Mozilla or System1 telemetry. Some users distrust the newer Waterfox’s data collection (even though it’s minimal) and prefer the "absolute zero" policy of builds from 2018-2019.
10.14 Mojave is the last officially supported. On 10.15+, you must disable hardened runtime or re-sign the binary (complex, not recommended). There are several legitimate reasons users seek out
Older versions of Waterfox (typically v56.x.x "Classic" or early v2020.x) are known for maintaining legacy features that modern browsers have removed.
The developer maintains an archive of releases. This is the only recommended source for downloading old versions. If you rely on a niche corporate intranet