One day after Uber updated its API to add ‘content experiences’ for passengers, the U.S. company’s biggest rival — Didi Kuaidi in China — has opened its own platform up by releasing an SDK for developers and third-parties.

Didi Kuaidi, which is valued at $16.5 billion following a recent $3 billion funding round and has an alliance with Lyft and other Uber rivals, gave an initial 30 apps access to its API — including chat app WeChat, Alibaba’s Alipay, Tencent Map and more — but now it is open to all.

The APIs include access to the “Hail a Didi Ride” button, but also cover its other services which include registered taxis, private cars and test drive services.

WeChat, China’s largest messaging app with over 500 million active users, already includes a feature that lets you book a Didi car from inside the messenger — much like Uber’s recent tie-up with Facebook Messenger in the U.S. — but now this functionality is likely to make its way into many more popular apps in China.

If you believe that platforms make the strongest grow stronger, then this news is likely to heap even more pressure on Uber in China, where Didi Kuaidi is the market leader by a long shot. UberChina, which recently landed funding at a $7 billion valuation, claims to have completed one million rides a day across its 22 cities since the summer of 2015. While China is expected to become its largest global market this year, according to Uber data, Didi Kuaidi is completing some seven million rides each day in the country. Indeed, this week it revealed that it did 1.43 billion rides across its seven businesses (not just taxi rides) during the whole of last year, including 200 million during December alone.

“This [annual] number is nearly twice the total number of taxi rides in the United States in 2015, and 1.4 times Uber’s global rides in the past six years since its launch in 2009,” a Didi Kuaidi spokesperson handily pointed out in an email to media.