Basic TvZ scouting and key timing


I have written about scouting in TvZ more than two years ago, and this is an update on it.

Share other tips you know in the comment. Correct me if I’m wrong.

This is meant to be a basic guide, so certain “advance” content is left out for parsimony reasons. An example of “advance” content is to spot the timing of Overlords. It is difficult to do it in the game itself, and it is certain hard to account for it in writing a basic guide.

The structure of this post will be something similar to the TvP scouting post, which focuses on what to scout for in different phases of the game. It will not cover reaction required based on the information gathered, as it is beyond the scope of this post.

Another thing to note is that, unlike other races, Zerg is much more “flexible” with production. It is relatively hard to deduce much beyond a certain point of the game. They can change their mind after you have scouted something. For example, you scouted that Zerg has been mining gas early on and you expect an attack to come, but Zerg may react to your scout by making Drones. It is hard to pin-point what Zerg is exactly doing and the timing of it, so please take that into consideration when reading.

Phase 1 – Basic Scv scout

This is based on the assumption that you play standard and scout at 15 supply, or something close. There are other Scv scout timings, but I will focus on the basic one.

The first thing you need to scout for is whether there is a Hatchery at the natural, and when it is built. The Hatchery should be close to complete when your Scv arrives at opponent’s natural in a two player map (if it is of “normal” distance) if it is a Hatchery first opening. These are the likely situations based on the Hatchery timing.

No Hatchery at natural

When there is no Hatchery at the natural, there are two main possibilities: one base all-in and proxy Hatchery. These are the common one base all-in

  • 6 Pool
  • 10 Pool (or 9 Pool)
  • Roach
  • Zergling and Baneling

6 and 10 Pool are usually not used in two player maps nowadays, because Terran will usually scout it and react accordingly.

The Scv should scout the main for the buildings and gas. A gas should have been taken if it is a one base all-in with Baneling or Roach. The Scv should see the Roach Warren if there is one, and it should be a Baneling and Speedling all-in if the amount of gas mined from the Extractor is more than 100 with Speed upgrading.

A proxy Hatchery can be Pool-Hatchery or Hatchery-Pool. The Spawning Pool will be completed if it is Pool-Hatchery, and it is completing if it is Hatchery-Pool. If the Spawning Pool is completed, the amount of gas mined is a telling sign if this is an all-in or a proxy Hatchery. The amount of gas mined for proxy Hatchery should be lower than for all-in. It can also be a no gas proxy Hatchery.

One base Mutalisk is possible, but that is very very rare.

Proxy Hatchery

Hatchery first

This is the most common opening in TvZ. If Zerg go for Hatchery first, it should be completing when the Scv reaches it. Next, check the main to see the Extractor timing.

There are three possible Extractor timing

  • No Extractor
  • Pool before Extractor
  • Extractor before Pool

No Extractor

For no Extractor, it can be an early third Hatchery or a gasless Pool opening. The obvious difference is clearly the timing of the Pool. Three Hatchery before Pool in TvZ is usually done on big map or Zerg scouted that Terran is doing a Command Centre first build.

If it is a gasless Pool opening, there are two main follow ups. One is a macro oriented opening with more Queens. The other is a +1/+1 Roach timing. Clearly, there are other openings, but these two are the more popular ones.


This is the most common one, and it is considered the “standard”. This can branch out to many possible builds, and it is hard to pin down which are the more common ones. But the key is to know whether speed upgrade for Zergling is researching after it has 100 gas. If the first 100 gas goes into speed upgrade, the upgrade should complete at around 5:45 to 6:00. You need to position your Reapers accordingly if you have any.

If the first 100 gas is not spent on speed upgrade, this should be a Roach attack. The Roach Warren is usually down at around 4:30. It is usually used as a reactionary build against Command Centre first.

Early Roach timing

Also, sometimes Zerg will not make Drones for a moment to get down an earlier Pool right after Hatchery, and this is good against proxy Barracks.


If the Extractor goes down before Pool, it usually means that Zerg plan to do an attack early on (it can also be an early Lair, but it is less common). By the time the Scv scouted the Extractor, it should have more than 50 to 100 gas mined already. If the first 100 gas goes into speed upgrade, and it usually is, the upgrade will be completed by 5:30 to 5:45.

The early attack can be almost anything like, Speedling only, Speedling and Baneling, Roach. The attack should commence at 6:00~ish.

Gas before Pool into Speedling timing

Gas before Pool into early Roach timing

Pool before Hatchery

Pool before Hatchery is quite common. Unlike 6 or 10 Pool, the Pool before Hatchery refers to a macro style opening with the Pool being built at 14 or 15. The Hatchery should be around 50% completion when the Scv reached it, and hence, the telling sign of whether it is a Hatchery-Pool or Pool-Hatchery is the timing of the Hatchery. When the Scv goes into the main, the first pair of Zergling should spawn around that time. This does not necessarily mean aggression from Zerg, as it depends on how many Zerglings are made at the point of time. It is decent against Command Centre on the low ground. The speed upgrade usually finishes later than the standard 6:00.

Pool before Hatchery

Phase 1.5 – More than 100 gas

The Hatchery, Pool and Extractor timing is basically all you can see at the Scv scout phase, and it is hard to deduce much based on the reason I stated right at the beginning of this post. However, there is still a small time frame that you will want to check the Extractor to deduce further what Zerg plans to do. This can be done by sneaking a Scv back in, which is often denied. Or, if you are doing a Reaper opening, you should be able to spot it at ease.

The common macro oriented builds involve getting speed upgrade early and a third Hatchery. Zerg will usually take Drones off gas (maybe leave one in), as they want the mineral for a third Hatchery and Drones. Subsequently, the Lair and Evolution Chamber will be down to move towards the mid game. Zerg may still put down a Roach Warren or Baneling Nest relatively early as defensive measure against certain Terran timing. For example, two base bio and various Hellbat timing. Nevertheless, the general approach is to get speed upgrade and take Drones off gas, then take a third Hatchery.

However, sometimes Zerg may throw a curve ball by doing an aggressive timing to catch Terran off guard even though the opening in phase 1 appears to be a macro opening. This usually involves continue mining of gas after Zerg have already mined 100 gas for speed upgrade, and the extra gas will be invested into aggressive tech like Baneling Nest and/or Roach Warren, or an early Lair. Thus, if you’re doing a Reaper opening, always sneak the Reaper back in to the Extractor to check if there are Drones mining gas at around 5:30. With that being said, Zerg may pull Drones off after they saw the Reaper going back in, and this means that you have to click on the Extractor itself to check the amount of gas mined.

Phase 2 – Third Hatchery

The rule of thumb for a standard macro game is that the third Hatchery is usually down at 6:00 to 6:15. Clearly, there is more depth to it, but I will just simplify it by saying it is 6:00. The timing of the third Hatchery provides much information about the mid game plan of Zerg. Assuming that Terran play a generally standard opening, and that means the build converges to a reactor Hellion convergent point, the first pair of Hellions is usually used to check the third Hatchery.

If the third Hatchery is at least 50% completed by 7:00, it was placed down at around the standard 6:00 time. There can be three possibilities

  • No third Hatchery
  • Hatchery is at least 50% completed
  • Hatchery is less than 50% completed

No third Hatchery

This puts you on red alert. It is either a quick Lair tech or a two base all-in.

Lair tech

It is almost certain to be a two base Mutalisk. Of course, it can be other Lair tech like Nydus Network, but you can assume that it is a Spire if you are unable to see the tech building. One thing to note is that a two base Mutalisk still gets a third Hatchery, but it is usually at around 7:00. Thus, when I say “no third Hatchery”, it can be considered as “Hatchery is less than 50% completed” depending on the timing of your Hellion scout.

The other telling signs are the timing of the Lair and the number of Extractor. The Lair timing depends on whether Zerg invest the first 100 into speed upgrade or Lair. If it is after speed, the Lair starts at around 6:00, and the Mutalisk should be out by 9:45. If it is before speed, the Lair starts as early as before 5:30, and the Mutalisk should be out by 9:00. While the Lair is upgrading, Zerg will take another three Extractor to make it four in total in order to produce Mutalisk when the Spire finishes. It is also common to upgrade Lair at 6:30 for Mutalisk in general in order to be safe against two base timing from Terran.

Another minor sign is that there is usually a Spine Crawler at the entrance of the natural. Although it does not necessarily tell you that it is Mutalisk, it is something to think about.

There is a two base Lair Roach timing with +1 attack that starts Lair at 6:30.

Two-base Mutalisk


This can be a variation of Speedling and Baneling, Speedling and Roach, and Speedling, Roach and Baneling. The first two are more common, as the third one usually involves putting down the third Hatchery (two base is relatively uncommon). Although I call them all-in, there is still much room for transition.

The Speedling and Baneling all-in can be used with various openings ranging from Hatchery-Extractor-Pool to Pool-Hatchery-Extractor. The telling signs are the early Baneling Nest and two Extractor. The attack hits at 7:30 to 8:00. This is the most common two base all-in.

Hatchery >50%

This is the most common. It can be a straight up macro game, and it can also be an all-in. It is hard to tell right at that point of time when the third is still building. The key is to check the third Hatchery when it has completed.

Nowadays, most all-in takes the third base at the usual timing, then put down the Baneling Nest and/or Roach Warren. The first thing to check is whether Zerg plan to all-in.


There should be Drones at the third Hatchery if Zerg do not go for an all-in. Also, the Lair should start at 8:00 to 9:00.


There are no Drones at the third Hatchery. This is usually Baneling and Speedling or Baneling, Speedling and Roach all-in.

Speedling, Baneling and Roach all-in

Speedling and Baneling all-in

Hatchery <50%

If the Hatchery is below 50% completion at 7:00, something is up. It can be two base Mutalisk like what I mention above, or some form of attack. The common all-in should put down the Hatchery at around 6:00, and hence, the Hatchery should not be less than 50% completed by 7:00. If it is, it can be the +1/+1 Roach timing. Thus, if the Scv scout in phase 1 saw no Extractor, and the third Hatchery is less than 50% completed at 7:00 in phase 2, it should be a +1/+1 Roach timing. Another sign is the double Evolution Chamber.

+1/+1 Roach timing


First, check the timing of the Hatchery at the natural, then check the timing of the Pool and Extractor. This should provide the base of what to expect in the early game. Next, check the amount of gas mined in the first Extractor, as it helps to deduce away what Zerg can do with the amount of gas obtained. The timing of the third Hatchery is a big factor of what can be coming. A standard third Hatchery timing does not necessarily mean it is not an all-in.

This is one of the most difficult posts to write. It is very hard to be precise with Zerg’s opening and build orders, because of the way the larva system works. I have a habit of not trying to appear to be too certain when it comes to saying “if you see X then it is Y” prediction. Thus, I edited away a lot of the “it can also be…”

Long story short, this is just a very basic guide, and by no mean exhaustive.

Special thanks to Zurgery, who helped me with many of my Zerg build questions.


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