Someone drops a video in the group chat: their cat, mid-nap, falling clean off a shelf.
Three replies land inside ten seconds — "ウケる", "ウケるんだけど", "ウケすぎ".
Not one of them has said the cat is funny. Grammatically, all three people have just announced the same thing happening to them, one after another.
The respectable, dictionary-entry version of this word is 受ける (ukeru), "to receive" or "to catch" — ボールを受ける, to catch a ball. From there it picked up a very ordinary extended sense: to go over well, to prove popular, to be a hit. お客さんに受けがいい, "it goes down well with customers", is completely unremarkable business Japanese. Nothing slang about it yet.
According to Japanese-linguistics research out of Hosei University, this "going over well" sense is where the slang usage is thought to start: as 楽屋言葉, backstage or greenroom jargon among kabuki and vaudeville-adjacent performers, for a line that lands — a gag that gets the house laughing. For a long stretch, ウケる described the audience's reaction to someone else's material. It was a verdict, handed down from the seats.
At some point — the research flags this as a comparatively recent shift and doesn't pin an exact year on it — the word jumped seats. Instead of only reporting whether a comedian's bit worked on a crowd, people started using it for their own reaction to anything: a meme, a dumb story, a cat falling off a shelf. ウケる stopped being a verdict an audience delivers and became something any one person can say, alone, about anything, to nobody in particular.
That spread bred a whole intensifier family: 激ウケ (geki-uke, roughly "massive hit"), 鬼ウケ (oni-uke, using the "oni" — demon — prefix that shows up all over current slang to mean "insanely"), and the deadpan 普通にウケる ("it's just straightforwardly funny", despite "normally" sounding like a downgrade). It is almost always written in kana rather than the kanji 受ける, a small, consistent visual fence that keeps the slang sense fenced off from the one about catching a ball.
One more wrinkle worth knowing: ウケる does not always mean something is good. Said flat, eyebrows up, about a friend's terrible decision or a stranger's outfit, it can land closer to "wow, that's absurd" — amused, not necessarily approving. Context and face sort out which one you are getting, same as half the words on this list.
English puts the funniness inside the joke: that's funny, as though humour were a property the thing itself owns. Ukeru puts it inside you. The verb literally means to receive, to be hit, to catch — so when something ウケる, grammar says it happened to the listener, not that the joke achieved something on its own. You are not rating the material. You are reporting an impact.