zerg flowchart

Dear Zerg players,

You can rattle off the proper defence for a 4gate - oh, get spines, roaches, easy. You know in theory that 3 queens will hold off a VR, and banelings hold a marine/scv all in.
But do you have trouble even IDENTIFYING the rush that's coming? Not sure how to interpret a 2 gas opening by Terran? How about a 10 pool with gas by Zerg? 10 pool without gas?

This miniguide is for you then, when I will provide a flowchart to guide you in your thought process off your scouting information. Asterisks (*) indicate additional notes.
Everything has been vetted by a top SEA zerg (aLtPiG!) so quality of information is guaranteed (if you don't trust me, that is. -sniff sniff- )

This guide does not tell you HOW to counter what is coming though, it just tells you WHAT can be coming based on scouting information. Thus, scouting is still (as always) very important, especially so for a reactionary race like Zerg.

IMPORTANT NOTE - I need to add a disclaimer - These are just MOST PROBABLE OUTCOMES, it does not factor in players who try to play mindgames on you , like Terran taking an early gas then suddenly killing you with proxy 2 rax or something. It also does not include non-typical builds like 7 rax all-ins, mothership rush, etc. though if possible I will try to mention them.
Another note - I am aware that there are other more comprehensive guides out there. This provides a simpler, more compact summary.

Zerg vs Terran
You'll typically scout with your 10 Drone, though often you may want to go with 9 Drone because Terran may try to do a fast wall-off, or on bigger maps you may scout the wrong way, etc. and reach late.

2 Barracks * - If you scout a Barracks/depot on the low ground (below his ramp) (i.e. Maka Rax), it’s likely to be some sort of 2 Barracks or even 4-7 Barracks cheese (if it’s walled off to prevent scouting). Of course, it is possible it’s just standard 2 Barracks and he’s just playing mind games with you. In this case, it’s VERY likely followed up with an expansion.

Marine/SCV all-in * - If no bunker rush comes off a 2 Barracks, something is fishy. Either your opponent is bad, or he is preparing some sort of cheese. Try to obtain whatever scouting information you can, such as with lings poking at his ramp to check Marine count, earlier OL sacrifice, etc.

1/1/1 tech tree * – There are too many options to list here, you need to go in again with a sacrificial Overlord or Overseer later on to know what he’s up to, though you can almost always expect Hellions to come harass in the early game assuming he didn’t go for a Barracks heavy build.

 
Mech play * - This can range from Marine/Tanks (likely if he has multiple Barracks too), Tank/Hellions, Mass Thors, etc etc. The best way to know is to send in Changelings / zerglings to catch a glimpse of his army composition.


Zerg vs Protoss
Against Toss in most cases you can send out a 10 Drone scout or even later, since the wall-in doesn't get done so early. However, if you're going for Hatch first you may want to scout earlier to spot a Forge so you know whether to be wary of cannons at your expo.
Remember that for Protoss, unlike Terran, you can keep your scouting Drone alive for much longer (until their Sentry/Stalker) so you should try your best to do that to get as much information as possible.

4 Gate * - One thing to note - Check if he is putting up a quick 2nd Gateway with his Cyber Core even if there's no 2nd Gas. If he does this, he could be going for a Stalker/zealot harass so be prepared. Watch what he chronoboosts!
Forge * - Be wary of cannon rushes in these situations, have an OL at your expo and a Drone follow his scouting Probe around. If his forge is on the high ground, he's bad. You better not lose.
No buildings * - If it's a singular pylon without gateway/forge, it could be a Nexus first (e.g. ST_Ace's favourite build in the recent GSL)  If there are no buildings at all, it's definitely a proxy of some sort.
Standard Gas Timing * - The Standard gas timing is shortly after the Gateway has begun. In most situations, by the time you reach their base the gas should be building already. 
2nd Gas * - The standard gas timing is shortly after the Cybernetics Core is down. An earlier 2nd gas may not mean anything; he may just be preventing a gas steal. Also, obviously if you steal his 2nd gas, it does not mean that he is definitely going for a 4gate. Just that if he HAS the option to get a 2nd gas and DOES NOT get it, it's most likely that he's going for a 4gate.
- There are so many things that the Toss can go for from here that it warrants a 2nd flowchart. Also, you should probably do an OL scout at 5+ minutes to get more information.


At this point you should have a zergling constantly running up his ramp to check what units he has (just poke at his gateway and he’ll probably reveal his ranged unit to come shoot you). You should try to keep an eye out for what he is using Chronoboost on too.

Stalkers * - Yes, even if you see Stalkers he may still be going for DTs or Stargate and the Stalkers are just to deny Overlord scouts.
4 Gate * - Yes, he may have got the 2nd gas to fake you out, and just stopped mining from it after he killed your scouting Drone.
If he had just got Zealots, it's a telltale sign of a gas heavy build, so try to sac an OL to confirm it.

Do note that these builds are typically 1 base builds - so if you don't spot an expansion after some time, you know something is fishy and should prepare for these.


Zerg vs Zerg
Probably the most complex and complicated match- up.. I hesitate to even start drawing a flowchart.Anyway, there are basically 2 stages of 'initial' scouting you need to do in ZvZ.
Stage 1 - To scout for your opponent's Opening Build
Stage 2 - To scout for your opponent's follow-up


Some Zergs don't even Drone scout in ZvZs, and can react with just their OL information. But I like to 9 scout just in case of any cheese and such.
Regardless whether you do Drone scout, what I urge you to do is this - with your 1st OL, position it such that you can see both the ramp and his expo.

Then there are also maps like Metalopolis and Shattered Temple where you can just scout sideways with OL and don't need a Drone scout to see everything your opponent is doing.

Stage 1 - What is your opponent opening with?

Early Pool * - There are a large variety of early lings harass builds : from 6-7-8-10 pool , and they can have different styles - e.g. with 1 or 2 spines, with drones, etc. Just remember to keep an eye on your entire base if you see an early pool THROUGHOUT the early stages of the game to look out for spines
Fast Banelings * - 10 pool banelings is a popular early pool build because it simply WILL do damage whatever you do (assuming you went standard pool or hatch opening) Just remember that your opponent sacrificed alot of economy just to do this, so don't be too worried if you lose some Drones to this
- Early pool with gas could also mean fast speedlings, though I've rarely seen that.

Speedling/Bling * - This either ends up in a sling/bling war, or they may do a speedling-expand build too. That's why you need your OL to be watching his ramp and expo, and why you need to scout Stage 2.

After Hatch first* - If he goes gas first, he's probably going slings/blings/spines for defence, if it's pool first it's probably lings/roaches/spines for defence.


Stage 2 - Scout for opponent's follow-up
This is as important, if not, more important than Stage 1. For example, seeing a pool before gas INDICATES a Roach opening, but it is very likely he may expand, or just simply be getting delayed speed, and if you assumed roaches you may react in a manner that's totally off.

Different from other matchups when whatever you see only INDICATES something but you can't really know for sure because you will be denied further scouting info, in ZvZ you can CONFIRM it, and this is done in Stage 2.

You will need to scout some time after the opponent's pool is done.
The best way to do this is to sneak a pair of zerglings into his base and run a round around to spot for tech.

SPECIAL TIP: There IS a tell-tale sign of what your opponent is doing even without entering his base. Remember that Overlord I told you to position at his ramp/expo? If more than 6 lings come out of his base, it's more likely than not to be a mass speedlings (maybe with +1) or a sling/bling attack.
But of course, best is if you can confirm it.

The outcomes are obvious according to what buildings you see, so I won't have a flowchart for this bit.
Roach Warren = Roaches, Bling Nest = Banelings, Evo Chamber = +1 Lings,
Lair = Mutas / Burrowed Roach Speed tech (any form of fast tech is normally accompanied with 129387 Spine Crawlers)