There are multiple channels of development of Firefox web browser. The Firefox 146.0.1 you are using is the current Release on the Release channel and is what you would get served if you download Firefox from say https://www.firefox.com/ There is also the Beta, Developers Edition and Nightly channels that people can use in testing things before it gets to Release. The Developers Edition is the same as Beta but with additional developer features. These are not really intended for regular uses but more for Testers and Devs in mind. The more unstable Nightly channel gets checkins and updates twice a day while there can be nine Beta builds of a version on Beta channel in testing. https://www.firefox.com/channel/desktop/ Release (currently at 146.0.1) < Beta (currently at 147.0b8) < Nightly (148.0a1, it always stays at a1) There is also the ESR channels short for Extended Support Release meant more for Enterprise users as they like longer term stability and updates support. These are not really intended for regular Firefox users in mind though there has been a few exceptions mainly in support old EOL OS's. The current ESR is Firefox 140.6.0esr For example the older Firefox 115 ESR (based on the old Fx 115 Release) currently at Fx 115.31.0esr is still being updated in support of the EOl Windows 7, 8, 8.1 and macOS 10.12, 10.13, 10.14 OS users. Yet Chrome/Chromium dropped support of these OS's back in early 2023.