https://www.gamespot.com/articles/starcraft-2-is-now-free-to-play-on-pc/1100-6454936/

Following the surprise announcement at BlizzCon earlier this month, StarCraft II is now free to play. Beginning today, November 14, PC players can jump into Blizzard's popular strategy game at no cost.

New players who are getting into StarCraft II for the first time will be able to play through the entire Wings of Liberty campaign for free. All of the current and upcoming co-op commanders are also free to play up to level five, while Raynor, Kerrigan, and Artanis will remain free to level up as much as you want.