On Wednesday, Google defended its business practices.

“While Google may be the most-used search engine, people can now find and access information in numerous different ways — and allegations of harm, for consumers and competitors, have proved to be wide of the mark,” the company said in a blog post.

Image Google’s European headquarters in Dublin. Europe has taken a more aggressive regulatory stance against American tech companies than the United States. Credit... Paulo Nunes dos Santos for The New York Times

Ms. Vestager insisted on Wednesday that she was on the side of “consumer choice and innovation” on the Internet. “We are not here to take the side of rivals — we are here to take the side of competition,” she said.

The action by Ms. Vestager highlighted once again how European regulators have taken a more aggressive regulatory stance against American tech companies than their counterparts in the United States.

Europe’s antitrust officials are reviewing low-tax arrangements granted to Apple in Ireland and Amazon in Luxembourg, and privacy watchdogs are looking into how securely companies like Facebook are protecting people’s online data.

Policy makers are investigating whether American Internet platforms like Amazon have too much control over how Europeans gain access to online services. And in response to a court order, Google in the European Union is having to remove some links in online searches in response to people’s declared “right to be forgotten.”

In the United States, the Federal Trade Commission investigated antitrust complaints against Google, but closed that inquiry in 2013 without reaching a formal finding of wrongdoing — despite an agency staff report, which subsequently surfaced, recommending stronger action. The action in Brussels on Wednesday is not expected to change Washington’s position that Google’s search business does not violate antitrust laws.