The actual mechanic itself has been seen in fighters as early as SF2, in few forms, and with each game finding more advancements, so do option selects. In the SF4 series, the game brings forth a new leniency towards input atop a more refined engine in terms of what you can do mechanically with your character, whether it be defensive options or offensive options. When you mix this with a technique like option selecting, tons of new and/or crazy option selects present themselves much more often than before. While it may not have the technical aspect of parrying (which also opened up a new layer of OS'), the new universal defensive option (back dashing, as only Necro had this option in the past), and reworked broader engine (albeit slower) of normals/specials/movement bring a larger scale of option selects at a more frequent pace.
The technique can seriously sway the outcome of a match in your favor. It allows you to smother defensive options against opponents trying to evade your offense, when normally they'd usually get away for free, and you'd have to work to get back in. On the other hand, there are a few option selects that enhance your defense as well, ultimately achieving the same goal: Keeping you in control of the match, and the pace. They allow you to dictate the match, and also provide a psychological edge. When an opponent is aware that you're option selecting against him, he'll usually panic when it comes time to use an option that he can no longer use. This will force many mistakes that you can easily take advantage of, without doing much aside from a few extra inputs.
However, it's important to know that using option selects will not instantly make you better. You'll still need to have a grasp on fundamentals, and timing. They will help you build these traits, though. They'll help you get a sense of the game's engine, as well, which will also help develop an idea of what you want to do in the game, and how to execute better.
I'm going to list a vast multitude of option select archetypes, and a few examples for each, with descriptive explanations and demonstrations for each one (because, quite frankly, if you don't know how they work, you need to see them to understand them fully).
Hyper Armor Absorb Option Select:
You can see the inputs in the video. A few of these OS are tough to time when recording, and are much easier to just do manually with a recorded AI string.
In the first OS, if Ryu does nothing on wakeup, you get ex bear run, but if he does something, it activates the ex kara cancel into ultra. Every character that has hyper armor has this option select ability.
With the hadouken one at the end, if they do not cancel the c.mk into fireball, you just get a bear run, where if they cancel into hadouken, you get a kara ultra. It's good now because of nerfed c.mk range.
Seth DP FADC OS:
This option select isn't really that great on whiff, but when the Seth users know what they're doing, it's usually not going to whiff. With that being said:
This OS is stupid. The fact that it works is pretty bogus, but the input is:
f,df+p ~ f,df+mp+mk ~ f,f,df+p
As seen in the video, on hit, Seth does a DP and follows up with another DP (the third DP can be done on reaction). However, when Ryu blocks, the second DP is FADC'd. This works because on block, the first and second hit of the DP are really fast, but on hit, you have a while to confirm the second and third hit of the DP, allowing you to do this.
Crouch Tech AA Triple OS:
This starts off as a very standard crouch tech OS (in the video, it's also delayed, so the crouch tech is also safe against DP if Yun choses to do that), which is just crouching and pressing throw.
When you do this, you'll notice you get c.lk when you don't tech. That's because you can't throw while crouching, only tech, so something has to come out when you press two buttons. This applies when you press three buttons as well LOL
When you press c.lk+c.lp+c.mk, the c.mk has priority over the c.lk, so instead of c.lk, c.mk will come out. This will catch early/fast dive kicks from Yun. Because c.mk isn't special cancellable, it makes it a very easy normal to option select with. Basically, as you can see in the video, c.lp+c.lk+c.mk ~ f,d,f+lp will result in a crouch tech that beats early dive kicks with c.mk, and when a late dive kick occurs, it makes the c.mk whiff, but because you did the motion for a LP fukiage, that immediately comes out and tags late dive kicks.
You don't have to worry about fukiage whiffing when you hit with c.mk, because as I pointed out, her c.mk doesn't special cancel.
Every character can do this, but some obviously have better AA normals than others.
Also, I did not find this OS, but it seems like a collective effort amongst the community to put together OS' like this one.
Another, simpler example of this OS utilizing an anti air normal instead of a triple os with reversal:
Just another example of crouch tech AA OS, to show the more universal side of things.
The input: c.lk+c.lp+c.hp.
Why it works? When you crouch tech, you get a c.lk because c.lk outprioritizes c.lp. However, c.hp outprioritizes both, so that will come out instead of c.lk. Essentially, you can replace c.hp with any normal, and use it outside of just anti airs. This if, of course, if your character isn't teching a throw via crouch tech.
Frame Trap OS:
These OS' are one of my favorites. What's going on is, Fei Long is doing c.lk into s.hp.
This doesn't combo regularly, but it is a very vicious frame trap. When Makoto presses c.mp or a slower normal after blocking the c.lk, you'll notice that Fei Long gets a counter hit s.hp, which then cancels into rekka. This is pretty much a basic frame trap.
However, when Makoto presses a slightly faster normal than c.mp, like c.lk or c.lp, you'll notice that she slightly interrupts Fei Long's s.hp frame trap, and causes it to trade. That's where the OS ultra comes in.
What you're doing is:
c.lk s.lp down, forward+lp ~ down, forward+3punch then confirm the rest.
Normally, Fei cannot combo s.hp into ultra. However, because it trades, he loses the recovery, while Makoto still gets all of the hitstun of a s.hp from Fei. This allows Fei to combo into his ultra.
What triggers everything is the s.hp into down forward LP ~ down forward 3P. When this is blocked or counterhits, the s.hp just cancels into rekka because it cannot cancel into ultra. You can do the ultra motion as fast as you want, because as long as one rekka comes out, ultra won't, because like s.hp, rekka cannot cancel into ultra at any point (lol). However, when Fei's s.hp is interrupted, that first rekka input is lost (because the timing was thrown off by trade) while the down forward isn't, and then the second down forward motion comes into play with 3P, triggering ultra.
Every character can do this, except for command grab ultras. Now, that doesn't mean every ultra benefits from it. Ken's U1 whiffs in similar frame traps, unless you're in the corner. It's up to you to find good ones for your char. I use an OS similar to this with Bison all the time (c.lk s.hp frame trap os u1), and some friends of mine do this with their characters as well. Knowing the input should help you find some of these with your characters, but make sure you find a proper frame trap for the situation.
Jump In OS:
These types of OS' are arguably the easiest to execute. I'll cut to the chase here, and just give the inputs for this particular OS and how they work:
The input here is:
jump down, forward mk~down forward +hp ~ land ~ s.mp - s.mk xx hands xx super.
You don't have to do the down, forward before you do the mk in the air, but I figured explaining it that way might make it easier for beginners to the concept at first, in which they can then move on to just doing jump~ mk~qcf qcf+hp~land. Alternatively, if that input isn't easy enough, try:
jump~ qcf qcf ~ mk~hp land.
This works because when j.mk is blocked or hits, there's a recovery for the move that exceeds the super input. However, when the j.mk whiffs, the recovery (altogether, mind you, including landing, hitstun, blockstun, etc) is much shorter, triggering the super motion that you input to come out.
These OS' are pretty common, and work extremely well in tandem with safe jumps, although you can do them off of any jump in. They also work well with resets into meaty xu's or jump ins as well, but they're generally not as safe as a calculated safe jump.
Chain Cancel OS:
These are, in my opinion, one of the easiest option selects to do, outside of jump in OS'.
What's happening here is Fei Long is getting the knockdown, and then meaties Makoto with c.lk and chains that into s.lp, which is then chained into s.lp and finally lined into c.lp xx rekka rekka rekka..
However, on c.lk whiff, ultra 1 comes out. This works because of the chain system.
A lot of characters can chain normals, most of them being light attacks. Certain normals can only chain into other certain normals as well, which is how you use the OS. It's simple:
c.lk chains into s.lp, but does not chain into s.mp or s.hp (or crouching for that matter). So, in the situation that you do c.lk s.3p, you will always get c.lp s.lp, even though you pressed 3 punch buttons. Now what you do, is you add the ultra motion before you press 3 punches, and you'll have an OS Ultra hidden in your chain. It comes out because when c.lk whiffs, and you go to chain into s.lp with 3punch, there's nothing to chain into the s.lp (because c.lk whiffed, of course), so ultra comes out.
The input, just for the sake of it, is:
c.lk ~ qcf qcf+3p ~ s.lp ~ c.lp xx rekka rekka rekka.
The timing is easy, just remember to do in in chaining timing. Pretend that 3P is jab, and just practice throwing in the two qcfs.
Other examples would be:
c.lk ~ c.lp~c.hk c.lp
As said above, c.lk chains into c.lp, but does not chain into c.hk, so when the c.lk hits, even though you're pressing c.lp and c.hk at the same time, c.lp is going to come out. However, when the c.lk whiffs, there's no c.lp to chain into so c.hk comes out.
Fei Long: c.lk ~ back, down, downback/back lp+lk, s.lp etc. When the c.lk hits, you get c.lp/s.lp (depending on whether you ended it in back or downback), and when it whiffs, you'll get lk flame kick. I only really abuse this OS when the opponents are cornered, because that's the only place it'll catch backdashes and slow startup i frame moves. (this principle applies to every DP, in which you would just change the motion before chaining into whichever normal you are chaining into; for instance, with Ryu, instead of of back, down, back+kick, it would be forward, down, forward+punch, and etc per character).
Fei Long: c.lp down, forward s.lp. This works similarly to the OS in the video, in which you're using the motion with the attack as a chain instead of pressing extra buttons. On block/hit, you'll get c.lk s.lp, but on whiff, you'll get c.lk rekka. Then confirm the other rekkas.
Normal Cancel OS:
These types of OS are also pretty easy, but can be risky to do if you have an overlapping super motion, especially when you're new to the trick.
However, these are simple enough to do that they're equally as simple to describe.
The input is:
c.mk ~ qcf +lp ~ qcf+3p.
In this video, Ken is doing c.mk into fireball after he scores the untechable knockdown. This is a meaty, and the c.mk is safe against all forms of Balrogs headbutt. It also goes underneath of his ex upper, and if you have meter, and sniff it out, you can safely cancel your c.mk into a HP DP, which will beat wakeup ex moves, while still maintaining an OS, but that's neither here nor there.
When Balrog does nothing, you get c.mk xx fireball. However, when pesky Balrog wakes up with what he thinks is a guaranteed counter ex headbutt, Ken's c.mk whiffs, and out comes ultra. Just like in the frame trap OS video, because c.mk whiffs, the fireball cancel doesn't come out, but the qcf from the fireball remains in tact, while the second qcf+3p does come out, activating the ultra.
It is basically a makeshift late OS, but because it functions slightly differently, I am calling it a normal cancel OS.
Command Manipulation OS:
The input is in the video, but I'll break it down.
What's happening here, is you're using one input (hcb+lk) and it has a different value in different situations. Typically, you're going to get a command grab.
However, a lot of players love to jump against characters with command grabs, because . . . Those command grabs hurt. This used to be a pain.
As you can see in the video, when Ryu doesn't jump, Yun dashes and command grabs him. However, when Ryu does jump (works against jump back as well), Yun gets a LK Nishou (upkick). This works because of the games leniency with inputs.
When Ryu jumps, it causes Yun to cross under him momentarily. When this happens, the half circle back motion becomes a down, forward motion on the other side, and because of the leniency, the forward motion you input while doing the half circle back auto corrects when Yun crosses under, and registers as the first forward of the DP motion on the other side. Because that comes first, the newly autocorrected down, forward (the down back in the half circle back) comes afterwards and completes the DP motion.
When Ryu backdashes, Yun dashes and command grabs him.
I should note out that a lot of characters can do something very similar to this, some of them being very similar and some of them being kind of similar. I know Makoto users have been doing it for a while. I'll give examples and inputs:
Makoto: dash hcb + kick+punch. I recommend using MK and LP/HP for the inputs. You can also kara this for certain characters who she won't cross under. That input would look like: dash f+lk down back +punch+kick, in which she'll kara forward to karakusa, or kara forward and have the input read as a fukiage.
Abel: Tornado Throw ~ Sky Grab OS: dash hcb+lp (works very similar to this)
Fei Long: Command Grab + Flame Kick dash hcb+lk (same as this, not so great though)
Seth: dash 360 ending with hcb + punch (If they jump, you'll get DP, if they don't, you'll get command grab: this is freakishly good when used in tandem with his fadc option select on DP)
Ryu: dash back, down, back +c.lp (I only put this in here to show that other characters can do this without a command grab; If the opponent jumps, Ryu will get an anti air DP, and if the opponent crouches, Ryu gets a c.lp to start a string)
Makoto Karakusa~Fukiage OS:
This option select is very strong for Makoto. She can do it just like Yun can on wakeup, and the fact that she can do it post hayate makes it very strong. Just like Yun, Makoto dashing forward against a jumping opponent (any jump) will temporarily make Makoto cross under and the hcb input becomes a forward, down forward input, causing the fukiage to come out instead of karakusa. Personally, this is much better for Makoto than it is for Yun, because it allows her to do a maximum punish against back dash or jump, and keep momentum while just about stunning her opponent.
The input is hcb+p+k.
Non Command Grab Input Manip OS:
This is also another example of command/input manipulation OSing.
I felt this was a required upload because previously, my examples all included command grabs with AAs even though I pointed out that most characters can utilize this option select.
So, I decided to show a situation in which Ken could utilize it.
The input is: hcb+p. You can replace punch with lk+lp, and you'll tech a throw and/or do a c.lk if you end the input on db, do a throw if you end the input on back (although the timing is strict to not get a tatsu), while still getting a DP under the circumstances of this OS.
Late OS' are generally harder for some players at first, while for others, they become easier than chain OS (because after practice, the margin of error becomes smaller).
What's going on here, is Vega is doing c.lk ~ downback, forward, back, forward+3k.
It's easy to tell if you mess these up, because you'll get c.lk ~ ultra on hit/block, instead of just c.lk on hit/block, which also makes them easier to practice (in my opinion). They're very simple to do, and all in all, the input is pretty straight forward.
Your aim is to do the c.lk meaty, and in the c.lk's recovery, input the ultra. The reason you want to do it in the recovery is because Vega's c.lk is special cancellable, and if you do it during it's active frames, you'll probably get a scarlet terror (somehow). However, because you can't special cancel the recovery, scarlet terror, or ex barcelona will never come out.
Late OS' are much easier to do with normals that cannot be special cancellable, so much so that I really don't feel they should be considered late OS (but they are). Doing a late OS on a normal that cannot be cancelled (balrog and makoto's c.mk come to mind), you would pretty much just do the motion for whatever you want to OS and the c.mk simultaneously.
The Sagat late OS applies pretty much the same as the Vega OS. I just threw it in there to give another example, and to show an example of what you could do after a blocked late OS.
With other forms of late OS, you would just replace the ultra with whatever else. For example, in the recovery of Vega's c.lk, you would press c.hk. On hit, or block, you can frame trap or kara throw, and on whiff, you c.hk comes out.
Same with Sagat. After that c.mp hits, it has a timing in which whatever you input won't come out. You have to learn this timing for all your characters normals in order to late OS, because you will be inputting the OS in the recovery of the normal on whiff. When they backdash, or i frame, that's when the ultra you are inputting will come out, where as on hit/block, you're still inputting that ultra at the same time, but it won't come out.
At first, it seems tedious, but after a while, it becomes second nature. So, in my opinion, it just comes down to learning your favorite meaties and normals in and out.
Throw AA OS:
This is mostly an example of a late option select, but thought it would be interesting enough to upload and give a brief write up on.
I would also like to point out that this OS requires a lot of confidence, because it feels very unnatural doing the DP in the middle of a throw. This is primarily a corner only deal, though. It is pretty good for offensive characters, especially those with command grabs that people feel the need to hold up on in the corner.
But, to explain it simply, what you're doing is you're pressing throw, and in the middle of the animation, you're doing an anti air, whether it be a normal, special, super or ultra. The only way the throw is going to whiff in this tick-throw situation is if they jump, or do an i-frame move, so in the event that they jump, they're in trouble.
Delay Crouch Tech:
The Delay Crouch Tech OS isn't different from the actual crouch tech OS aside from the delay. However, I felt the technique itself was crucial enough to get its own video and run-down as opposed to vanilla crouch tech osing. As you're most likely aware, a regular crouch tech OS is basically a c.lk, because you can't throw while crouching. When an opponent tries to throw you, on the other hand, the game will read the throw input as a tech. As said, it is done by crouching and pressing throw. LK has higher priority than LP, so a c.lk will always come out instead of c.lp.
That is pretty much the entire concept. But it never just ends there.
As it turns out, throws in SF4 have a seemingly large window in which they can be teched. This allows you to delay crouch tech, which opens up a whole new window of offense (or defense). Basically, a reversal such as Yun's LK/HK Nishou Upkick has a startup window (5/8 Frames respectively). If you delay your crouch tech by that many frames, you will safely throw out a poke 8 frames later upon their wakeup, and not eat a reversal.
Throwing seems like it would thwart this simple shred of genius, but it doesn't. Again, this is largely due to SF4's super lenient teching window.
Now, unlike a lot of specific reversal setups, you don't have to learn how to crouch tech against every reversal. You should, however, learn a comfortable setup/timing for delay crouch tech against each type of reversal in terms of startup, i.e a delay crouch tech against 3 frame reversals, 4 frame reversals, 5 frame reversals, etc.
Oddly enough, delay crouch tech is much easier against 3 frame reversals than it is against 8 frame reversals because the delay is relatively short, whereas the delay against 8 frame reversals may seem slow, initially.
This shows a grounded version of the delay crouch tech against a 3 frame reversal instead of an 8, and it also excludes the jump in portion, so you'll get an idea of how it looks without jump setups.
Delay crouch teching is a very powerful tool because it allows you to apply pressure without worrying about much. It gives the mirage of confident aggression to your opponent, which will make them challenge you in foolish ways that will get them punished. These often lead into bread and butter combos, or resets into throw or overhead/low, especially if you have meter and the means to use it.
Obviously, its biggest perk is the safety blanket from your opponents wakeup. If timed correctly, it'll stuff their normals, tech their throw and block their i-frame depending on what they do. As you can see, it really cripples your opponents options. And, like other normals, you can option select off of a delayed crouch tech with anything you want.
The other huge benefit to this technique is the fact that a crouch tech hits low, and if this technique is used off of an empty jump, your opponent will likely block high if they're not going to try a reversal, which leaves them wide open for a low crouch tech to start your BNB.
Fireball/Special Trap OS:
You could say this is similar to the kara OS, but this actually lends itself to the kara OS. It works almost the same.
Again, no character can have two separately input fireballs on the screen at the same time except for Juri. This allows every other fireball character to do a trap option select with a reversal against ways to escape meaty fireballs. It doesn't have to be a reversal, though. In fact, you can OS anything in the input of your second fireball, and it'll come out instead of a second fireball if the first fireball is still on the screen (only possible if the meaty timing is off, or if your opponent makes it whiff via i-frame reversal).
The input for this would be:
backthrow .. fireball .. slight pause .. down, forward+p~downforward+p
An alternate input would look like this:
back throw .. fireball .. slight pause .. down, forward+p, down, forward+p (this is easier, but I don't recommend it with supers that overlap fireball/dp inputs).
If you wanted to OS a s.hp instead of a fireball, you would simply just do down, forward+hp after the first fireball, but make sure you go neutral or hold back when you press HP, or you'll get a f+hp. Ryu's fs.hp will beat ex chicken wing in this situation.
This OS can be used defensively, and does not require a knockdown. It doesn't require meaty, either. This OS can technically be used with any special which is why I included "Special" in the name, but a very small few of the specials in this game can beneficially utilize this (demon flip, fireball, dive kick, etc).
Kara Option Select:
While this OS primarily fits Sagat's plan the best, any character that can cancel a normal into a fireball and a reversal can utilize this (Sagat, Ken, Guile, etc). It may not be as beneficial to them as it is to Sagat, though. This is huge for Sagat, especially considering that it's the easiest for him as well, and his dominant range.
Just like in the Fireball Trap OS, the same rules apply here: Outside of Juri, no character can have two fireballs on the screen at once. The fact that you're kara-ing forward just shortens the time in which you have to wait to input your option selected DP with fireball, but also requires you to press more buttons at a slightly faster pace. The input for this is:
throw .. down, forward+punch .. down, forward (hold)+lk~punch/kick~downforward+punch
Just can also use the alternate input in the fireball trap OS.
The reason this is more effective with Sagat than any other kara OS, and fireball trap OS is because Sagat usually doesn't need a meaty at all, even though it helps. His fireballs have low recovery, his kara has great range (both of them, actually, as you can replace f+lk with f+hk in this OS, and it is much more effective outside of meaty situations), his followup fireball is usually really fast (enough to combo fireball into fireball), and because of the range, his DP stuffs almost every attempt to escape (whether it be jump, or special move). You don't even need to include the DP with f+hk because the f+hk will catch jumps.
Another example of this against Balrog:
As you can see, it even stuffs out Balrogs hyper armor (which works like a focus attack for other characters in this situation).
Okay... It's not technically a kara OS, but it's an OS Kara ;)
input: c.mp down forward+lp > lp, f+mp, downforward+lk+hp
Alternatively, you can do c.mp down, forward+punch, f+mp+lp~lp, downforward+lk+hp within the fireball.
This utilizes the normal cancel OS more than kara, so for more info, refer to that section.
Trade Option Selects:
I feel that these have become more common on high level play with characters like Akuma (see Tokido) and Fei Long, because they involve a situation where you've already committed to doing a move (most likely an anti air/reversal), so adding an extra input really isn't going to hurt at all. In fact, you pretty much only benefit from it. There's no downside.
They're really effective when you're using a move that has juggle properties, because in SF4, everything seems to have a tendency to trade in the heat of battle (when you need it to not trade =( ). When juggle properties are involved, this means you can follow up, but it usually has a small window in which you actually can follow up and normally requires fast reaction, unless you were fishing for a trade to begin with. OSing cuts this out.
Let's cut to the chase; The input is:
f,d,df+P (DP) followed by a smooth hcb+p all in one. You can do it fast, but because it's not as consistent as a smooth timing, I usually do DP~hcb+p,hcb+p (I do the red fireball twice) if I want to do it fast. It's like pseudo-double tapping.
This can be done with any move that can actually juggle/followup a traded move that puts your opponent in juggle state.
Guile Trade Ultra OS:
This example is just to show that charge characters can also do it, as well.
downback, upback+kick ~ f,b,f+ppp
Note, dash U2 os in this trade actually isn't tough if you know how to dash ultra, and it's actually beneficial for those rare trades that send Guile back a little further. I would also like to note out, that while a little tougher, Guile can also OS his U1 in this trade.
This is essentially just two chain OS in one string. I only uploaded it to show its purpose (against players who try to get around OS'), and that it's not necessarily hard or extravagant.
Input: c.lk, down, forward+lp, forward,down,forward+lp, s.mp xx HK DP.
It doesn't catch Rose's focus back dash, but it keeps Yun right on top of Rose, and will beat out her c.mp if she tries to throw it out immediately after back dash.
For more on this OS, refer to the chain OS section, as it is literally just two chain OS' in one.
Akuma Double OS:
This is a double OS that utilizes Jump In OS and Normal Cancel OS. The fact that proper true block strings (jab jab in this case) cannot be interrupted once initiated (demon flip > jab) allows Akuma to setup a vicious OS against teleport mash. This is just an example, as upon confirming the hit, Akuma can devastate his opponent with the amount of meter he has in this video. As you can tell, this video was uploaded a bit earlier than my actual OS videos, but it's there for a reason.
forward, down, downforward+k > lp,lp,f+lk+hp .. c.lp c.lp s.hp xx down, forward+lp,lp,downforward+lk+hp.