Windows Phone seems to be chasing the app stores of Apple and Android and now holds a gamut of 30,000 apps.

In the Microsoft blog, Todd Brix, senior director of Windows Phone Marketplace announced, “nearly 30,000 Windows Phone app and game titles available today will also run on Mango.”

The Windows Phone Marketplace has seen steady growth with the number of apps, reaching 11,500 in March and 25,000 just last month and now it has hit a milestone of 30,000 apps.

When compared to Apple’s 500,000 apps and Android’s 250,000, Windows Phone 7, Microsoft’s first major update is lagging behind.

After HP decided to shut down all WebOS products, Microsoft has launched campaigns on Twitter to get WebOS developers to make apps for Windows Phone 7.

Brandson Watson, Microsoft’s senior director of WP7 development, said he got response from more than 500 developers in a day.

Last year, a report from the IDC analysts suggested that Windows Phone Marketplace could be the third largest app store by the middle of 2011, behind Apple and Android.

Microsoft has always shown more concern about the apps themselves rather than the number of apps, with Watson saying that its more about quality over quantity.

Microsoft also mentioned in the blog that it’s final version of Windows Phone SDK 7.1 will arrive by the end of September, which will provide the users with tools needed to develop applications based on Windows Phone 7 and Windows Phone SDK 7.1

“New and existing titles optimized for Mango features like fast app switching, background audio, multiple and double sided Live Tiles, better Search integration and more will begin publishing in a matter of days,” Brix wrote in the blog.