Japan's antitrust regulator said Google used tactics that limited Yahoo Japan’s ability to compete in targeted search ads, and it promised to keep monitoring the U.S. firm.

From 2015 to 2022, Google, held by Alphabet, blocked Yahoo Japan from accessing technology needed to receive targeted ad revenue from searches on mobile devices, the Fair Trade Commission said. Alphabet changed its conduct as soon as the watchdog flagged the practice and has promised to give Yahoo Japan access to keyword-tied targeted ad tech, the FTC said Monday.

"Google’s actions had a significant effect of limiting competition,” FTC official Saiko Nakajima told reporters. Yahoo Japan is a subsidiary of LY, which operates the country’s biggest messaging app Line. The Japanese watchdog will continue to monitor the situation and reserves the right to reopen its investigation into Google, Nakajima said.

That promise was part of the FTC’s first-ever administrative action against Alphabet, which came with no penalty.

Antitrust enforcers across the globe are increasingly worried that a small number of large companies control many of the world’s key technologies. Regulators fear that companies like Microsoft, Google, and Amazon are using their technology and scale to frustrate or buy out potential rivals and remain on top.

Alphabet is fending off complaints at home and abroad that it uses unlawful tactics to block competition. In the U.S., it faces a $700 million settlement after dozens of state attorneys general filed complaints that developers have to go through the Google Play app store to reach users.

Japanese authorities are also probing Alphabet to see if it asked local smartphone makers to prioritize its search services on their devices.