Added an option to print only the current page from the print preview dialog.
Firefox now supports partitioned service workers in third-party contexts. You can register service workers in a third-party iframe and it will be partitioned under the top-level domain.
Swipe to navigate (two fingers on a touchpad swiped left or right to perform history back or forward) on Windows is now enabled.
Firefox is now compliant with the User Timing L3 specification, which adds additional optional arguments to the performance.mark and performance.measure methods to provide custom start times, end times, duration, and attached details.
Searching in large lists for individual items is now 2x faster. This performance enhancement replaces array.includes and array.indexOf with an optimized SIMD version.
Stability on Windows is significantly improved as Firefox handles low-memory situations much better.
Touchpad scrolling on macOS was made more accessible by reducing unintended diagonal scrolling opposite of the intended scroll axis.
Firefox is less likely to run out of memory on Linux and performs more efficiently for the rest of the system when memory runs low.
Available via the internal updater: Help / About Firefox
Windows 10 Pro (64-bit), Windows Defender, MBAM4 Pro, Windows Firewall, OpenDNS Family Shield, SpywareBlaster, MVPS HOSTS file, WinPatrol PLUS, SAS (on-demand scanner), uBlock Origin, Microsoft EDGE, Firefox, Pale Moon.
[I believe computer-users who sandbox (Sandboxie) are acting prudently.]