Adobe AIR is a runtime environment that allows developers to create rich internet applications (RIAs) using web technologies like HTML, CSS, JavaScript and Adobe Flex. AIR apps can be deployed and run as desktop applications on Windows, Mac and Linux. AIR provides access to local system resources like the file system and ability to work offline. While AIR allows creation of cross-platform desktop apps using web skills, it has some limitations around extensibility and database access. Popular apps created with AIR include TweetDeck, eBay Desktop and Google Reader.