Firefox now givesWindowsHints to ample set content process priority levels, meaning more processor time spent on the tasks you're actively working on, and less processor time spent on things in the background (with the exception of video and audio playback).
To improve battery life on dual-graphics-card macOS machines, Firefox now tries more aggressively to switch back to the more power-efficient GPU for WebGL content when able. Firefox also works harder to avoid switching to the high-power GPU for one- Off transient uses of WebGL.
Finder on macOS now displays download progress for files while they’re being downloaded.
Added support for the Web Authentication HmacSecret extension via Windows Hello on systems running the Windows 10 May 2019 update or newer.
As previously announced in thePlugin Roadmap for Firefox, the "Always Activate" option for Flash plugin content has been removed. Firefox will now always ask for user permission before activating Flash content on a website.
Firefox no longer loads userChrome.css or userContent.css by default. Users who wish to customize Firefox by using these files can set the toolkit.legacyUserProfileCustomizations.stylesheets preference to true to restore this ability.
Some users in the test channel can already see the switch of the process priority manager function named dom.ipc.processPriorityManager.enabled. From the feedback of the test results, the process priority manager has not been greatly improved in terms of browsing performance, nor has it become worse, but the use of system resources has been greatly improved.
According to Mozilla, lowering the background process priority and allowing the operating system to prioritize the foreground tabs is worth a try, so that the foreground process can get more processor time when needed.
It's important to note that this feature will not be enabled in the tabs for playing media content, because Mozilla hopes that sites like YouTube will continue to run in the background without interruption.
On systems running Windows 10 May 2019 updates or updates, the new version adds support for the Web Authentication HmacSecret extension via Windows Hello.
In terms of Apple's system, in order to improve the battery life of dual-graphics macOS notebooks, Firefox can now switch more aggressively back to more energy-efficient GPUs for WebGL content. Firefox also works harder to avoid switching to high-power GPUs. The Finder on macOS now shows the download progress when the file is downloaded.