Major League Baseball has tinkered around with the idea of making a few rule changes to speed up the pace of the game and draw more interest. The league has been testing these ideas in the Atlantic League. The two leagues have a three-year agreement in place for the Atlantic league to experiment with the new rules to better gauge what type of impact, if any, they might have on the game.
The newest rule the Atlantic League has been asked to test? Stealing first base. Per Jacob Bogage of The Washington Post:
In the second half of the season, the league will allow batters to steal first base: Any pitch on any count not caught in flight will be considered a live ball, and a batter may run to first base, similar to a dropped third strike.