According to the release notes, it brings:
- This beta is now available in 54 languages – get your local version.
- Added a new Private Browsing Mode.
- Added functions to make it easy to clear recent history by time as well as remove all traces of a website.
- New support for web worker threads.
- Improvements to the Gecko layout engine, including speculative parsing for faster content rendering.
- Removed the new tab-switching behavior based on feedback from users