Amazon.com will start letting users make purchases within the applications sold in its online store, matching a feature offered by rivals Apple and Google.

The company today In-App Purchasing (IAP) service, making it easy for Amazon Appstore developers to offer digital content and subscriptions for purchase within apps and games that are available on Kindle Fires and other Android devices.

Amazon Appstore?s In-App Purchasing service is simple for developers to integrate and helps monetize their apps and games. Developers including ZeptoLab, Disney, Glu Mobile Inc., Storm8, Social Gaming Network, Gameloft, G5 Entertainment Inc., and top publishers like Conde Nast, Dow Jones and New York Post, have already integrated Amazon Appstore?s In-App Purchasing API.

"Amazon Appstore's In-App Purchasing service enables developers to generate more revenue from their apps," said Aaron Rubenson, Director of Amazon Appstore. "In-App Purchasing is simple to integrate and gives developers access to millions of Amazon customers who are already familiar with Amazon's 1-Click payment system. Many of Amazon Appstore?s customers have shopped with Amazon before and they trust Amazon?s easy payment process, which leads to higher conversion of developers? in-app content and subscriptions."

By making it easier to charge for items within apps, developers may be more likely to write software for Amazon?s store. The feature also provides extra revenue for the retailer, which will take a 30 percent commission from every in-app purchase.

Amazon is trying to catch-up with Apple and Google with its app store. It currently has about 34,000 apps. Google and Apple have more than 450,000 apps apiece in their stores.