What it means
When something is all the rage, everybody wants it and cannot stop talking about it, the must-have craze of the moment. The rage here is the old sense of a passionate fashion, a collective frenzy for the latest thing. From a dance to a gadget to a diet, if it is all the rage you will see it absolutely everywhere until the next one comes along.
Usage examples
"Bucket hats are all the rage again, everyone at the festival had one on."
"Those chunky trainers were all the rage last summer, now nobody touches them."
"Those chunky trainers are all the rage again, everyone's wearing them."
"Cold brew coffee was all the rage that summer, every cafe had it."
"That little matcha spot's all the rage right now, you can't even get a seat after noon."
Where it comes from
This one goes back to an older use of rage meaning a hot fashion or craze, not just anger. By the late 1700s and 1800s, people were already using it for whatever fad had the whole room losing its collective head. All the rage simply means the thing everyone’s suddenly wild about.
