A little pedantic, but: this will tell you if a poem is shaped like the common English conception of a haiku, but it won't tell you if this is a haiku, because a haiku is more than just counting syllables.

Aside from the fact that "syllables" is not exactly the unit being counted in haiku, there are also considerations of theme, tone, and a sort of "open-ended-ness" – among other considerations.

This article served as my introduction to the actual complexities of haiku: https://forgottenpoets.substack.com/p/haiku-thursdays-one-pl...