If you're new to Archive of Our Own, the word 'kudos' is probably the first piece of jargon you hit. A kudos is simply AO3's version of a like: a single button at the bottom of every work that lets you tell the author, in one tap, that you enjoyed what they wrote.
Kudos are also the closest thing AO3 has to a popularity metric, which makes them genuinely useful for readers. Sorting a tag or fandom by kudos is one of the most reliable ways to surface the fics a community has loved most.
How kudos work
You can leave kudos on any work whether or not you have an account — logged-out readers show up as 'guest' kudos. You can only give kudos once per work, and you can't take them back, so the count only ever goes up.
Because every reader can leave them with a single tap, kudos counts run far higher than comment counts. A beloved long fic might have tens of thousands of kudos and only a few thousand comments.
Kudos vs comments: which matters more?
Kudos measure reach — how many people enjoyed a fic enough to tap the button. Comments measure engagement — readers who took the time to say something specific. Most authors will tell you a thoughtful comment is worth more to them than a kudos, because it's a real conversation.
As a reader, you can use both: kudos to quickly find what a fandom loves, and comments to see what people actually thought before you commit to a long read.
Frequently Asked Questions
Can you give kudos without an account?
Yes. Guests can leave kudos on any work; they appear as a generic 'guest' rather than a username. You can only leave one kudos per work.
Can you remove kudos on AO3?
No. Once you leave kudos they're permanent — there's no un-kudos button, which is why the count only ever increases.
What's a good number of kudos?
It's entirely relative to fandom size and fic length. In a huge fandom a popular fic might have 20,000+ kudos; in a tiny one, a few hundred is a hit. Use kudos to compare fics within the same fandom, not across the whole site.