Two companies in the tech industry are merging as Microsoft acquires mobile cross platform development company Xamarin in an effort to help developers push universal apps across platforms.

After a few years of being a subject of rumors, Microsoft has bought Xamarin, a 4-year-old San Francisco-based maker of software development tools.

While the deal's terms were not disclosed, The Wall Street Journal says in its report that a person close to the deal said that the price was around $400 million to $500 million.

Executive vice president of Microsoft’s Cloud and Enterprise Group Scott Guthrie writes that "with today’s acquisition announcement, [Microsoft] will be taking this work much further to make [its] world-class developer tools and services even better with deeper integration and seamless mobile app dev experiences."

He also says that the combination of Xamarin, Azure, Visual Studio Team Services and Visual Studio offers a "complete mobile app dev solution" that gives developers everything they need to create, test, deliver and instrument mobile apps for any device.

"We are really excited to see what developers build with it," he says.

Microsoft has a plan to preserve Xamarin's branding. It also intends to hire the company's 350 employees, including co-founders Miguel de Icaza and Nat Friedman.

Friedman says the deal opens up a much bigger opportunity to reach quite a few developers with its tools. He adds that Microsoft is planning to integrate the technology of Xamarin into its developer kit to offer “accelerant” to the firm's business.

“We get to hit a lot more people and a lot more apps,” says Friedman.

Xamarin already has over 15,000 clients in the likes of Dow Jones, JetBlue, Kellogg’s, Flipboard, Bosch, GitHub and Microsoft.

For a few years now, Xamarin has partnered with Microsoft in a number of projects. Xamarin tools work with the company's Azure, Visual Studio, Enterprise Mobility Suite and Office 365.

To date, the company is offering a number of services, including the following below.

Xamarin Test Cloud – a service provides a way to test apps on real devices

Xamarin Platform – a software that extends the C# programming language to write native apps for a multitude of platforms

Xamarin University –  a service providing online classes

Xamarin Insights – an analytics service