1-3-1 — Modified the effective date that baseballs shall meet a NOCSAE performance standard. (Effective January 1, 2020).

6-1-3 — Modified an element of the pivot foot requirement.

Officials’ Signals — Created a signal for a 3- or 4-person mechanic to indicate the direction of rotation to the umpiring crew.

Officials’ Signals — Created a signal for a game umpire to alert his or her partner of relevant information.

https://www.nfhs.org/sports-resource-content/baseball-rules-changes-2019/