Firefox Developer Edition 67 -

: To speed up page loads for sites like Amazon and Instagram (reported by Mozilla to be 40–80% faster), Firefox 67 began deprioritizing non-essential features and delaying setTimeout until after the page starts up.

: Developers can now track all CSS modifications made within the browser and copy either the full set of changes or individual rules directly. JavaScript Debugger Improvements : Firefox Developer Edition 67

: Added support for importing JavaScript modules dynamically. 4. Privacy & Security Understanding in depth the profile per installation feature : To speed up page loads for sites