Mozilla has shipped Firefox 57 Beta and Developer Edition yesterday. As you may already know, this release is called Firefox Quantum that delivers significant performance improvements to the browser thanks to a brand-new CSS engine codenamed Stylo and numerous bottleneck eliminations.
There are only a few site compatibility changes in Firefox 57 because Mozilla developers have been very busy with Project Quantum. However, Stylo may introduce unexpected page layout regressions, so please make sure to test your site with Developer Edition before the final release in November.
Firefox 56, on the other hand, is scheduled to ship this Friday. As usual, we’ll monitor several sources to try finding potential regressions. Both for Firefox 56 and 57, let us know via Twitter or other channel if you find any problems!