Ács entered the world stage, playing against elite players in several tournaments. In 2002, he participated in the FIDE World Chess Championship, where he progressed as far as the final sixteen. Ács' performance in this tournament was exceptional, particularly his victory over grandmaster Vassily Ivanchuk. Two years later, at the 2004 FIDE World Chess Championship, Ács reached the third round but was defeated by Michael Adams.
In 2013, Ács moved to Malta and subsequently played under their flag. Despite now representing Malta, Ács still resides in Budapest, Hungary, and is a coach at the PDC Sport Consulting , contributing to the growth and development of the chess scene in Malta and internationally.
He has not been very active in competitive chess since 2008, as he shifted his focus more towards teaching and promoting the game.