HALF MOON BAY, Calif. — Alexa is multiplying. And that’s exactly what Amazon wants.

The smart speaker assistant, which debuted four years ago with the tech company’s Echo device, has gone from a handy gadget for streaming music to a ubiquitous home tool, able to do everything from switching on the lights to ordering an Uber.

Amazon announced recently that it had sold more than 100 million Alexa devices. And the company is all in. Last fall, it unveiled more than a dozen assorted devices that tap into the voice assistant, including a microwave and a wall clock.

Dave Limp, Amazon’s senior vice president for devices and services, said Alexa was “at scale” and had gained the most traction by making parts of daily life more convenient.

“We started with the home; we’re now adding the car,” Mr. Limp said at The New York Times’s New Work Summit last week.