Anne van Kesteren for Mozilla says:
Effective immediately, all new features that are web-exposed are to be restricted to secure contexts. Web-exposed means that the feature is observable from a web page or server, whether through JavaScript, CSS, HTTP, media formats, etc. A feature can be anything from an extension of an existing IDL-defined object, a new CSS property, a new HTTP response header, to bigger features such as WebVR. In contrast, a new CSS color keyword would likely not be restricted to secure contexts.
In other words, if your site isn’t HTTPS, you won’t get new web tech features. Holy jeepers. The reasoning is the web should be using HTTPS, so this is our way of beating you with a stick if you try to use fancy features without going HTTPS first.
It’ll be fascinating to watch the first major feature drop and if they stick to their word here. The web dev forums of the internet will overflow with WHY DOESN’T grid-gap WORK WITH MY FLEXBOX? (or some likely coming-soon feature) questions and the answer will be: talk to your server team. What if they drop container queries behind this? That would be a hilarious devastating tornado of developer fury.
