More than 45,000 developers are now using the Microsoft Bot Framework, Microsoft CEO Satya Nadella said Monday. This makes it one of the most popular ways to create a bot, in part because of its versatility.

The Microsoft Bot Framework allows bots and machine learning programs to be created not only for Skype but also for Facebook Messenger, Kik, and other chat platforms.

By comparison, roughly 34,000 developers are making bots on Facebook Messenger, a company spokesperson told VentureBeat on Monday.

Messenger VP David Marcus used the same figure two weeks ago when discussing the total number of developers using Messenger. (Wit.ai bot engine is the designated framework for Facebook Messenger.)

Microsoft and Facebook Messenger both announced the opening of their chat platforms in the beginning of April. By mid-July, each platform had roughly 20,000 developers using its bot framework. But as we head into fall, Microsoft has taken the lead, at least in terms of the total number of developers using each framework. Bots for Microsoft and Messenger can be made on several platforms, not just within their own frameworks.

A key characteristic of the Microsoft Bot Framework, Nadella said, is its openness.

“We’re taking an approach where any bot you build is not captive to any one conversational canvas. It’s available everywhere,” he said on stage Monday at Microsoft Ignite, a four-day enterprise tech conference in Atlanta.

Nadella has delivered bold statements about the future of conversational computing at a number of developer gatherings.

“Pretty much everyone today who is building applications, whether they be mobile apps or desktop apps or websites, will build bots as the new interface,” he said this summer at Microsoft’s Worldwide Partnership Conference, in July.

Nadella has also gone so far as to call chat “the new interface,” a UI that will be as important to computing as the graphic user interface.

Google may have leapfrogged both tech giants with its acquisition of API.ai, a bot-building platform that allows developers to make bots for more than a dozen platforms and which is currently used by more than 60,000 developers. The API was acquired last Monday, a day before the release of new Google chat app Allo, and Google has hinted that the API.ai platform will be used to bring bots to Allo.

Of course, the number of developers on board is only one measurement in the battle for chat platform dominance that’s taking place between companies like Apple, Google, Facebook, and Microsoft.

In another key step forward, Facebook became one of the first major chat platforms to allow payments within a bot.

Updated Sept. 27 at 11:31 a.m. Correction: The original version of this article stated that Wit.ai makes bots for Facebook Messenger only. Wit.ai is owned by Facebook, but code from the open source repository and the Wit.ai natural language understanding API can be used to make bots and software for multiple platforms.