Google turned to the Court of Justice of the European Union (CJEU) after the General Court in 2021 threw out its challenge to the fine levied by EU antitrust chief Margrethe Vestager in 2017.
It was the first of three penalties for anti-competitive practices that have cost Google 8.25 billion euros in total in the last decade.
Google lawyer Thomas Graf said the European Commission had failed to show that the company's different treatment of rivals was abusive and that different treatment alone was not anti-competitive.
"Companies do not compete by treating competitors equally with themselves. They compete by treating them differently. The whole point of competition is for a company to differentiate itself from rivals. Not to align with rivals so that all are the same," he told the panel of 15 judges.
"Qualifying every different treatment, and in particular different treatment of first party and third party businesses, as abusive would undermine competition. It would impair the ability and incentives of companies to compete and innovate," Graf said.
Commission lawyer Fernando Castillo de la Torre dismissed Google's arguments, saying the company had used its algorithms to unfairly favour its price comparison shopping service, in breach of EU antitrust laws.
"Google was entitled to apply algorithms that lower the visibility of certain results which were less relevant for a user query," he said.
"What Google was not entitled to do was to use its dominance in general search in order to extend its position over comparison shopping by promoting results of its own services, and embellishing them with attractive features and apply algorithms that are prone to pushing down the results of rivals and showing those results without attractive features," he said.
The CJEU will rule in the coming months.
This case and two others involving the Android mobile operating system and AdSense advertising service, however pale in comparison with the ongoing EU antitrust case into Google's lucrative digital advertising business where regulators in June threaten to break up the company.
The case is C-48/22 P Google and Alphabet v Commission (Google Shopping)
($1 = 0.9353 euros)
