Google regularly tussles with regulators over taxes, privacy, and competition, but the latest battle, which came to a head Wednesday in Europe, may be the biggest challenge yet to the company’s mobile strategy.

Regulators are going after Android, the key to Google’s shift from a company serving information and ads on personal computers, to one that beams this content to billions of phones, tablets, and smart-home devices. If charges stick, the company will find it harder to grow ad revenue, control costs and make money from mobile gadgets in Europe.

“To date, this is the one that should not be completely dismissed,” said James Cakmak, an analyst at Monness Crespi Hardt & Co. “Android is an extension of Google and its touch-point to virtually every non-iPhone user in the world. Anything to potentially threaten that is a risk.”

Europe said Wednesday that Google’s main strategies for making money from Android are anti-competitive. At issue are contracts requiring handset makers and wireless network operators to pre-load Google services, like Search and its Chrome browser, on Android phones that use Google’s Play app store. Google also offers financial incentives for Android partners not to install other search engines on their devices, the regulator said.

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