I found the following definition: "Game theory optimal (GTO) poker is an umbrella term players use to describe the holy grail of no-limit holdem playing strategy, by which you become unexploitable to your opponents and improve your winrate."

The book "Harrington on Cash Games" teaches you what hands to play preflop in each position, and gives you percentages of the time you should bet, raise, check and fold with them. It does the same for the most common situations on the flop, turn and river. The author mentioned the reason behind his approach was to make one hard to be read and exploited by the opponents.

My question is: Was "Harrington on Cash Games" basically a GTO book, and the newer publications have taken the concept further tweaking the percentages and going more in depth with each hand? Is that what GTO really is?

GTO is the strategy that results from 2 perfect players exploiting each other while mitigating how much they get exploited as much as possible.

The most functional way in which people use the word GTO is in opposition to the word Exploitative, in this dichotomy:
GTO: Every aspect of a strategy that uses its range composition to deceive Villain from knowing the hand we're holding.
Things like using the same sizing with certain parts of your betting range on a given spot, being careful to neither bluff too much nor too little, being careful to not station nor overfold... are all ideas that could be seen as "GTO oriented".
Exploit: Every aspect of a strategy that uses Villains range composition, Villains strategy at a given point in time, and the hand we're holding at that time, to calculate the maximum Expected Value line.
Ex: Villain has a lot of top pair here. He likes calling with top pair a lot. I have a set -> Betting is higher EV than checking.

Thank you very much for your reply. So mostly under GTO fall the play adjustments made at the table in order to be hard to read by all the others who are watching you, and Exploit plays are the adjustments you are making while playing against a particular opponent based on what you already know about him. The only reason you would make only GTO adjustments in a particular hand is if you know nothing about the opponent and there is nothing to exploit. Did I understand it right?

You should specially keep in mind GTO concepts whenever playing someone who will be observant about your tendencies over long periods of time and who is good at exploiting those tendencies.

Also whenever you don't know anything about which line is highest EV, it makes sense to mix it up because there is no drawback. But, most newbies mix up things that are clear blunders, they just don't know yet. So in my opinion, as a beginner, is to stay away from GTO for a while until a bunch of concepts have been understood and processed

Here's a quote from "Modern poker theory" a very respected recent book on GTO:

I'd recommend buying the book if you're really interested in GTO.
If you're a beginning poker player I'd recommend forgetting about GTO for the next 1-2 years and just focus on learning basic strategy.


Understanding what GTO actually means and is in poker is fairly complicated.

We know what GTO means, but we don't know what a GTO strategy looks like.
It's too complicated for any computer to fully calculate at the moment.

For a human playing GTO in poker is as impossible as it would be to beat the best chess AI's.
(Human's haven't been able to beat them for years and the AI's are still getting better.)

I was under the impression that GTO was a different strategy recently invented, but now, with your help, I think I understand, it's not a strategy at all, it's just like a new folder that contains concepts as old as the game is, but with adjustments tweaked using computer simulations. Extremely useful to know and apply, the more the better, but you still need to be a good all round poker player in order to be profitable. Correct?

Thank you for the book quote and recommendation. As aner0 suggested, at my level I need to focus on fundamentals rather than GTO. I am happy that now at least I have an idea of the meaning of GTO, while before I was completely bamboozled.

GTO is an actual strategy, Nash Equilibrium. It wasn't invented recently, it has existed for a long long time, but with computers we are so much closer to see how it looks than in the past.
Since humans can't and won't ever be able to play the complete GTO Strategy, when we say someone is playing "GTO" we are talking about his strategy being designed around not allowing villain to exploit him.
GTO assumes Villain has a perfectly adaptable strategy, while Exploitative assumes Villain has a completely static strategy. The truth is somewhere in between.

Thank you very much for all your help. Basically I've been learning GTO-type strategy all along, since virtually any poker book contains ideas about how to make yourself harder to read and less easily exploitable. I just didn't know it was called that way.

And, if you're posting in here, leaving money on the table. You make money by exploiting the weaknesses of opponents, not by playing defensively and worrying about the other players who may not know how to exploit you in the first place.

Once you get to a level of play beyond BQ where you might be against a whole table who can exploit you and aren't giving much away, the GTO play isn't to play "GTO" either, ducy?

I remember reading Harrington on Cash Games like 12 years ago when it came out. It definitely wasnt GTO, more like an exploitative strategy to beat 25NL-100NL at that time. Its probably still a good starter book to get going in the micros.

Harrington was always a little bit ahead of his time as far as advocating for mixed strategies. Even HoH 1 talked about using a randomizer (he mentioned the second hand on his watch) to choose between a mixed strategy in different spots.


Edit: I read Harrington on Online Cash Games, which came out a couple years later and focused on online 6max.

After giving some thought to your answers to my questions, I think I have a better understanding of what GTO is. Please read and tell me what your opinion:

The Nash equilibrium is an older concept involving two astute players trying to outwit each other until they reach an equilibrium, an impossible task considering the complexity of the game and the limited human lifespan. But in recent years, with the advancement of computing power, it became possible to run a simulation that could eventually archive all the possible poker moves and make them available for analysis, leading to a whole new strategy that is unbeatable on long term, and rivaled only by itself. That is GTO, “The Wholly Grail”.

Even though the GTO library is not finalized yet, there is plenty of data already available, included in the so called solvers, so a player could input a particular situation from the table into a solver and see what the optimal next move would be according to GTO, and learn from that. Also, from the data analysis resulted conclusions and patterns, available for study in books and articles.

And, solely for the purpose of categorization, the kind of poker moves/actions designed to exploit your opponent are called “exploitative”, and the actions designed to protect yourself from being exploited are called “GTO”, which IMHO is such an unfortunate choice and was the root of my whole confusion. Since the exploitative moves are just as much part of the GTO library as the protective ones, why call the protective moves “GTO” instead of “protective”, and avoid all the confusion?

One last thing: When Daniel Kates said in an interview “I'm playing closer to GTO now than a few years ago”, he most likely meant he is now playing in a way that is harder to be exploited by his opponents, not that he is actually playing in a way that resembles a computer using GTO software, correct?

You nailed it in the sense that people use the word "GTO" to mean differnt things, they just don't know it, and yes, true GTO is exploiting his GTO counterpart as much as he can.
When Daniel Kates said the GTO thing, he probably meant that his playstyle alligned with what a solver would output more closely than before

GTO is not explotive except that it allows you to profit from your opponent's mistakes.


And lol at “The Wholly Grail”.

Thank you for all the time you've spent explaining things to me. It's guys like you who make the forums a valuable resource. I am in debt to you since you did not learn one thing from all my silly posts, while I have learned a lot from yours.

Thanks, it's $200

Do you accept food stamps?

I think the easiest way to explain GTO vs Exploitative to someone that has no idea of either is going through how each relates to the game of Rock Paper Scissors.

GTO:
Players each know the others strategy & each play in a way that the other knowing their strategy will not result in an advantage for their opponent. The strategy becomes play Rock 1/3 of the time randomly, play Paper 1/3 of the time randomly and play Scissors 1/3 of the time randomly. Think about it for a second or two and you will realize that if I tell you that this is going to be my strategy and I follow through with it, you will be able to do no better than doing the exact same.

Exploitive:
Knowing the others strategy, one takes advantage of knowing that. Lets go back to Rock, Paper, Scissors again. Lets say for example that I like Rocks and don't care for paper or scissors because I was traumatized as a child in school. I tell you I am going to play Rock 100% of the time. If you stubbornly follow GTO to the letter, you continue to Play each 1/3 of the time randomly. This will clearly not get you the best results against me. What you should do is play in an exploitive way. Knowing that I play Rock all the time you should choose to play Paper 100% of the time and you will win 100% of the time.

Eventually I will wake up and realize that I am losing all the time and start to mix in something other than Rock. If I am at all observant I will realize that because I told you that I am going to play rock all the time and now I notice you playing Paper all the time I should play scissors next which will result in a win for me. As each player gets better at observing the other and adjusting accordingly both will eventually hone in on playing GTO which is randomly playing 1/3 of the time Rock, 1/3 of the time Paper & 1/3 of the time Scissors

Obviously there is a lot to putting each into practice and when to use each etc, but hopefully that gives you a basic idea of the difference between each one.