Scouting is the act of revealing (either with a unit's line-of-sight or Scanner Sweep) remote areas of the map to gain information about the opposing player(s).
General Scouting Purposes
Scouting is a fundamental part of SC2. Almost any Build Order requires some sort of Scouting in the first 3 to 8 minutes. If your Opening is vulnerable to Cheese you should scout. Most Build Order offer help, when to scout and what to scout for.
Thus, what is of supreme importance in war is to attack the enemy's strategy.—Sun Tzu, The Art of War
General Scouting Purposes:
- To uncover enemy gameplay decisions
- To reveal the expansions of the opponent
- To learn the location of enemy units
- To facilitate the prediction of tech choices
- To assist game-play decisions
Worker Scout: Pros and Cons
In higher leagues to scout with a worker (see Early Game Scouting) is a controversial debate among many players. E.g. Welmu did not scout duckdeok in two games (Belshir & Newkirk), playing against each other at 2013 WCS Season 2 Europe for 6 minutes. He scouted for Proxy-Buildings, though.
- A worker scout costs about 90 minerals for two minutes of scouting.
- Early Game: Players in higher leagues often choose not to scout with a worker, if they play a safe Build Order. E.g. 2Gate-FE (PvP)
- Zerg can use their Overlords to scout.
- Players in lower leagues often lack the skill to defend Cheese or react properly to it (without scouting).
- If a Terran plays CC-First, he cannot play Proxy-Rax or any kind of Reaper-FE.
- In PvP one can click on the Nexus to check the energy. E.g. a 4Gate saves the energy.
- Early-Pool-Play (like 6Pool or 10Pool) often counters fast expansions in the lower leagues.
- ZvP: In higher leagues some Zergs play Triple-Hatch-Before-Pool, if the scout a Gate instead of a Forge. A Drone scout is the fastest way to check it on larger maps.
Note: In lower leagues a worker scout is recommended, if you die to Cheese often. Scouting a Pylon at your Natural early in the game, might indicate a Cannon Rush. Scouting allows you to take the necessary steps to defend Cheese like that. If a Protoss plays some kind of Gate-FE (like YufFE), a Cannon Rush is very unlikely.
Early Game Scouting
Scouting in the beginning of the game consists of sending out a Drone, Probe, or SCV to find your opponent's location, as well as to learn their opening build order and game plan. When scouting your opponent, you should consider the following:
- Proxy - lack of buildings in base.
- Cheese - lack of workers and more unit-producing structures.
- Double Gas - would indicate a fast tech build.
- No Gas - usually indicates a fast expand.
- Structures - the type of unit producing structures will give an indication of what build or what units the opponent will use.
- Placement - the placement of the buildings can indicate if the opponent will turtle or play aggressively.
Zerg players usually send their initial Overlords to find their opponent's base, making sure to position them close to a cliff or edge if there is a possibility of ground-to-air units. Drones can also be used to build an Extractor in the opponents base, canceling it before it finish building, continue scouting and repeat. Canceling a building results in a 25% loss of the cost. The prolonging of denying a geyser by canceling and rebuilding even up to 4 times would only result in a loss of 25 minerals and can be very worth it.
Mid/Late Game Scouting
As the game progresses, higher-tech scouting units come into play.
- After creating a Barracks, Terran can upgrade their Command Center into an Orbital Command which can cast Scanner Sweep on a portion of the map, revealing any enemy units and buildings. That, however, is often not the best choice because Orbital Command energy can be used for MULEs instead.
- Terran players can also float their buildings for scouting. Their low speed is compensated by a large amount of hitpoints for relatively low cost. A well-executed example of this tactic is employed by TLO in TLO vs Nony on Lost Temple. The Barracks is comparable to the cost of a Scanner Sweep ( 150 + SCV time off the mineral line, vs. 270 from a MULE over the next 90 seconds), but has the advantage of being able to linger over the base by moving to the fringes of the map and brought back again for a peek when ranged defenders are away. One disadvantage to this is that you give your opponent information about your build. For example, if you are going for a Barracks / Starport heavy build and use your floated Factory to scout, you are telling your opponent that you required a Factory for something, but do not plan to use it.
- When Lair tech is completed, a Zerg player can upgrade Overlord speed, enabling Overlords to fly quickly into an enemy base and reveal a glimpse of that enemy's current buildings and tech.
- After the Lair tech, Overlords can also be upgraded to Overseers, who can use the Spawn Changeling ability to walk a unit through an opponent's base or to follow a hostile army.
- Burrowed units can also be used to scout.
- The Protoss detection unit, the Observer, is most commonly used for scouting in the mid game. Once Gravitic Booster has been researched it is a small and agile unit. The first goal is to get an Observer into your opponent's main base, to scout their army composition. After that, or if you're blocked, spread the Observers throughout the map to scout for army movements. One patrolling Observer is a good way to scout for hidden expansions.
- With the Sentry upgrade Hallucination, you can summon a Phoenix or an other high mobility unit do scouting for the duration of the spell. In Wings of Liberty, this is a cheap (100 ) and safe way to scout your opponent's base without having to worry about losing a unit. However, if you do not get a Robotics Facility any time soon, Hallucination would be cheaper and faster than getting a Robotics Facility and an Observer. There is also the benefit of potentially deceiving your opponent of a false tech route. In Heart of the Swarm, Hallucination no longer requires research.
- Another option for mid to late game scouting is the Dark Templar. Even though it should first and foremost be viewed as an offensive unit for the Protoss, if it is blocked by an Overseer, Missile Turret or Observer it can be left outside the opponent's choke to catch lone SCVs, Probes or Drones and scout army movements. It should also be mentioned that this is a far less economical choice to make.
Active and Inactive Scouting
This is a translation of a German video created by "creativelearningtv". Definition:
- Active Scouting
- If a player uses Micro to scout an opponent, he uses "Active Scouting". E.g. jumping with a Reaper into the enemys base.
- Inactive Scouting
- All things which helps to improve awareness of the Minimap. E.g. taking all Xel'Naga Towers on the map.
- Send a unit (worker) to scout the enemy's base.
- Quote Day: "Scout the front!" with a unit/worker.
- Attack with some units, e.g. Blink-Stalker or Banshees or Mutalisks
Active Scouting helps to scout buildings and unit compsotions. It helps to react to your opponent and plan the next few minutes of the game. It sometimes exploits weaknesses, too (Artosis-Pylon).
- Place units below ramps or other strategic points on the map, e.g. Zergling, which is attacked, when your opponent moves out.
- Block or watch your opponents expensions with units, e.g. Widow Mines, Zerglings or Pylons
- Work in progress ...
If a unit is attacked (Zergling at ramp) a player usually gets an acoustic and visual signal. Really good players constantly take a look at the Minimap.
Studying the Meta-Game
The act of scouting occurs before the game even begins by researching possible enemy builds. Doing this research will increase the effectiveness of scouting and improve your ability to counter the enemy. Studying the Meta-Game and knowledge about Build Orders, will not only make it easier to scout and identify your opponent's build, it will make it easier what to scout and when to scout. Doing so will increase the effectiveness of scouting and improve your ability to counter the enemy. Knowing almost all possible builds of your enemy will not only show you what he has right now, but what your opponent will have in a few minutes from then.
Look in the Strategy section of Liquipedia for each of the three races (Terran Strategy, Protoss Strategy, Zerg Strategy) and read all of the major builds the enemy is likely to perform against you. Try not only to understand the basic build order but also the unit composition and the idea behind the build itself. In most builds, you will want to scout your opponent at around 10 to 15 consumed supply - it's during this time the enemy should have made his first tech choice. Determine beforehand what the enemy should have at this point for each build. Doing so will help you understand weaknesses and possible alterations to standard build orders.
If you are in a higher league, you can use Replay Websites and check out the replays or google for your favorite player (Replays). Download 5 to 10 replays which contain your main race (3 from each of your possible match-ups is best). Notice the build orders each player uses. Watch how the professionals execute their build order and timings against the opponent. Actively participate in watching the replay. At every decision that the professional makes ask "Why would he do that?" In every attack, noticing the flaw each player makes is twice as important as noticing the player's success. You do learn something from success, but you will always learn much more by failure.
Why is this not advised for lower leagues? Player in lower leagues may not understand anything what a professional player does. And they have many problems, like
- too many minerals
- Time Supply Capped is too high