The update, described by developer Blizzard as the game's "most feature-laden patch to date", will introduce new social features and an arcade mode.
Patch 1.5 overhauls the game's mod suite, and brings improved custom game visibility, ratings, reviews, game instructions and screenshot support. Blizzard has also released its own art creation tools to aid mod creation.
Starcraft II's new social features include the option to resize and save chat windows, log back into the last chat channel used, and connect with others nearby based on IP address. Blizzard said that the latter feature may not land with Patch 1.5, but will arrive before the expansion pack.
The StarCraft II: Heart of the Swarm is yet to be given an official release date, but is expected to land sometime this year. Patch 1.5 is also yet to be dated.
StarCraft II: Wings Of Liberty was released for PC in 2010.
> Read Digital Spy's review of 'StarCraft II: Wings of Liberty'
> Read Digital Spy's interview with 'StarCraft II' senior designer Jonny Ebbert
Watch gameplay footage from Heart of the Swarm below: