Firefox ESR is the release channel crafted for enterprises, owing to their inability to upgrade browsers for workers every four weeks; but instead, Mozilla issues ESR that is supported until approximately once a year, and its replacement appears with several-week overlap.
Mozilla adopted the concept nearly a decade ago, from concerns by large organizations over the supposedly fast release schedule of Firefox browser, and IT admins balked at testing and switching to a new release every few weeks.
Therefore, ESR tends to address that by allowing only the separate security updates Mozilla releases (and distributed in every-four-week schedule as used by the standard browser channel). While other new features are not introduced to ESR version during its year-long duration.
Enterprise users, however would always "catch up" on feature and functionality changes when next ESR is released.
How Firefox ESR next transition works
Mozilla now uses an eight-week overlap during which it would release both the previous ESR (designated "n") and replacement ("n+1"), in order to give enterprises time to test and roll out the next ERS.
And enterprises that have been using Firefox ESR 68 since the summer of 2019, which end is near, as the next ESR is v. 78; Mozilla will refresh both ESRs starting from July 28 and August 25, to ESRs 68.11 and 78.1 appearing on the first date, and ESRs 68.12 and 78.2 on the second.
The next release cycle, which is slated for September 22, will see only ESR 78.3, while ESR 68's support will come to an end on that same day.
What's next for Firefox 79?
As expected, during an ESR transition, Mozilla usually issues two builds on a three-release cycle to give IT admins ample time to test and deploy the next static-for-a-year browser.
And Firefox 78 also began the culling of OS X 10.9 (Mavericks), 10.10 (Yosemite) and 10.11 (El Capitan) from support, which automatically shift users of those outdated operating systems to the Extended Support Release (ESR). Meanwhile, the next Mozilla upgrade, Firefox 79, will be released on July 28, 2020.