- Mode summary(src)
In Co-op Missions, players take on the role of various commanders from the StarCraft universe, each of them possessing unique abilities and upgrades and bestows special bonuses on their armies. Players are able to battle through a series of special scenarios together, leveling up their commanders’ capabilities as they progress. New abilities and units are unlocked as one progresses through the mode, along with gaining experience. Which missions are played can be chosen or randomly determined for bonus experience, and the computer opponent will utilize different strategies in each mission. Each race is available for each mission.
Difficulty can be adjusted in the mode, and a matchmaking system is utilized.
Each commander gains experience independently. Upon completion of a mission, a commander will gain experience—the harder the difficulty setting, the greater the level of experience gained. As each commander levels, they will unlock additional units to call forth into battle as well as upgrades to existing abilities or traits. Each day you can earn 10000 bonus experience with the first victory of the day for one commander.
The events of the missions in Co-op Missions take place during the End War. Specifically, after the second mission of the Legacy of the Void campaign, and before the epilogue missions. However, Blizzard officially considers the game mode and events that take place in its missions non-canon, which grants them more freedom in gameplay design.
Mutators are a Co-op Missions feature that were introduced in Patch 3.3. They are special conditions designed to add variety to missions, and vary on a weekly basis.
Mastery Levels were introduced in Patch 3.3. With mastery levels, any experience a player earns on a maxed out level 15 commander will go towards earning Mastery Levels, up to a maximum of 90. Each level grants the player a point that they can spend on each of their level 15 commanders to increase their power. This includes spending points to increase attack damage, reducing deployment time of abilities, buffing health of structures, and so on. With up to 90 points available, the number of options can't be filled out for every command, but the points can be reset and re-applied at any time prior to starting a match.
Ascension Levels were introduced in Patch 3.17. Ascension levels give players no in-game strength or bonuses, but allow players who have hit mastery levels to also level for cosmetics, including emoticons and sprays. There are a total of 1000 ascension levels, each requiring 200,000 experience.
List of Commanders
List of Missions
- Assault missions
- Defensive missions
- Control missions
The mode was originally called "Allied Commanders." It was changed to "Co-op Missions" in order "to better communicate the design intent." Blizzard staff later explained the name was causing confusion with Archon Mode, where two players work together commanding one force in melee gameplay; the name change to "Co-op Missions" was simpler and better conveyed to players the type of gameplay they can expect.
The mode was created to provide a more accessible multiplayer mode for StarCraft II, as the developers believe that the standard multiplayer has a reputation for being inaccessible and time consuming. It is intended for players mainly interested in singleplayer, but provides a more open-ended and social experience than a standard campaign.
When designing a mission in the mode, map layout is the first issue addressed. As two players are involved in a mission, the map size must reflect this. Adapting a mission from the game's singleplayer, base size is increased, expansions added, and the paths of choke points are generally widened. Once the layout has been solidified, enemy unit placement and composition are looked at. The main issue is making sure the enemies are strong enough to deal with the power of combined player armies and commander abilities. Finally, the developers spend a ton of time implementing and tuning the main and bonus map objectives as well as the attack waves. When choosing which maps to import from the game's campaign, the mechanics that would be well suited to the mode are looked at first.
When choosing a commander for implementation, a variety of factors are considered. These include the popularity of the character, and ensuring a relatively equal distribution between the number of commanders available to the three races. Each commander, even of the same race, is designed to look artistically unique.
More maps and commanders will be added to the mode post-launch. Karax was released for free December 15th, 2015, but future commanders will require purchase. As of "Miner Evacuation," it is intended that newer maps have elements of randomness (e.g. objectives spawning at random locations), helping in replayability.
Leaderboards will be added at some point in the future. Each time a player completes a mission, they'll get a score that reflects how efficiently they completed that mission. Once they've completed all the missions, a score on the leaderboard will be assigned. Separate scores will be given for mutators. The leaderboards will reflect the choice of commander and the difficulty on which the map was played. They're expected to be implemented in mid-2017. They are intended to allow indirect competition between players. Leaderboards will be refreshed in conjunction with the release of new maps and commanders.
- Tychus Findlay
- Ariel Hanson 
- Matt Horner 
- Arcturus Mengsk
- Valerian Mengsk
- Egon Stetmann (Serves as a map advisor, but commander data in the editor)
- Gabriel Tosh
- Horace Warfield
According to a poll conducted by Blizzard, 16% of StarCraft II players' primary interest in the game is in Co-op Missions (as of January, 2017).