In little more than a year, China’s city sidewalks have become crowded by the brightly hued bicycles of dozens of rival bike-sharing startups. As the bikes lure throngs of riders, investors have taken notice: The two largest bike rental companies, Ofo and Mobike, have raised a combined $1 billion from funders, including Yuri Milner’s DST Global and Sequoia China.

While investors are attracted by the companies’ growing revenue from rides, they are equally interested in the potential for generating cash from advertising on the apps that consumers open to use the bikes. As tens of millions of users generate hundreds of millions of views, the companies’ mobile apps deliver traffic that is unusual for an offline product.