As a dialect of Clojure, it's a dynamically typed language. But its designer has expressed interest in eventually adding static type checks via a gradual typing system¹:

> I mentioned that a native Clojure is the first step toward my dream language. Indeed, it doesn't stop there. jank will always be a Clojure dialect, but it will also optionally support more. Features like gradual typing (maybe linear typing), more explicit memory management, value-based errors, and stronger pattern matching, to name a few, improve upon Clojure. This will allow another axis of control, where some parts of the program can remain entirely dynamic and garbage collected while others are thoroughly controlled and better optimized. That’s exactly the control I want when programming.

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1: https://jank-lang.org/blog/2025-01-10-i-quit-my-job/

Oh man, as someone who used to contribute to a statically typed lispy language this would be the dream for me.