What happens with perfect play
On the classic 3×3 board, perfect play from both sides leads to a draw. That means if both players always make the best available move, neither can force the game to a win. The first player has an advantage in tempo, but the second has enough resources for accurate defence.
This does not make the game boring. On the contrary, it is exactly why tic tac toe works so well for learning strategy. You can see very quickly what happens when one player is precise and the other is not. A draw under perfect play demonstrates the strength of defence, not a lack of depth.
Why you can still win often in real games
Because real people do not play perfectly. They rush, they fail to check every line, they choose the wrong opening cell or they underrate the diagonals. In that world the winner is whoever makes fewer mistakes and exploits the other side's slips better. So in practice the question is better phrased not as "can I always win" but as "can I win noticeably more often". And there the answer is much more positive.
If you are more attentive than your opponent, take the strong cells more often and never ignore a compulsory block, your mathematical "not always" turns into very good statistics over a long run. That is felt especially clearly against beginners and against players who attack aggressively without controlling the board.
In that sense the pieces on winning and on common mistakes are far more useful than hunting for a mythical guarantee.
Why the question is different on bigger boards
On 4×4 and larger boards a game becomes much less rigidly predictable. There are more options, perfect defence is harder and the positional struggle lasts longer. That does not mean an automatic win for the first player, but it does mean the room for mistakes and for creativity grows noticeably. So on bigger boards "can you always win" becomes an even less useful question, while "can I find more practical chances" becomes a very apt one.
This is why many players see the larger boards as a more tactical, less drawish version of the same game. There an overall view of the board and the ability to build long lines matter far more than simply holding a short defence.
A more useful way to think about it
Rather than hunting for an absolute winning formula, set yourself more practical goals. Learn not to lose to crude mistakes. Get more precise in the opening. Develop a better feel for the moment when attack has to give way to defence. Spot double threats earlier. These are real skills, and they improve your results.
That approach promises no miracles, but it makes your play stronger. And it is far more useful than the idea of a "secret way to always win", which on an honest 3×3 board simply does not exist.
Test it in a live game
Open several games in a row and try to play as accurately as you can. You will see that without mistakes a draw arrives often, and that wins appear exactly where someone loses precision.
FAQ
Can you always win on 3×3?
No, not against perfect play. With accurate defence the game usually heads for a draw.
Why do strong players win more often, then?
Because opponents make mistakes in real matches, and a strong player exploits them better.
Is it easier to win on bigger boards?
There are usually more practical winning chances there, because the line is longer and the board is harder to defend perfectly.