https://www.pcgamer.com/overwatch-is-free-to-play-this-weekend-starting-from-now/

Overwatch is free to play this weekend, and once again "this weekend", from the "Overwatch is free" perspective, begins on Thursday. Which means it's live right now! 

The free weekend includes the full Overwatch roster and map lineup in modes including Quick Play, Custom Games, and the Overwatch Arcade. Players will level up and earn loot and unlocks in the usual fashion, and if you purchase the game during or after the free weekend, any progress you've earned will carry over. You will of course need a Battle.net account (which is also free) to take part.