Consequently, Flex applications can be developed using standard Integrated development environments (IDEs), such as IntelliJ IDEA, Eclipse, the free and open source IDE FlashDevelop, as well as the proprietary Adobe Flash Builder.

In 2014, the Apache Software Foundation started a new project called FlexJS to cross-compile ActionScript 3 to JavaScript to enable it to run on browsers that do not support Adobe Flash Player and on devices that do not support the Adobe AIR runtime.

[8] Flex uses MXML to define UI layout and other non-visual static aspects, ActionScript to address dynamic aspects and as code-behind, and requires Adobe AIR or Flash Player at runtime to run the application.

[9] Macromedia targeted the enterprise application development market with its initial releases of Flex 1.0 and 1.5.

The core Flex 2 SDK, consisting of the command-line compilers and the complete class library of user interface components and utilities, was made available as a free download.

Adobe based the new version of Flex Builder on the open source Eclipse platform.

Flash Player 9 incorporated a new and more robust virtual machine for running the new ActionScript 3.

Major enhancements include integration with the new versions of Adobe's Creative Suite products, support for AIR (Adobe's new desktop application runtime), and the addition of profiling and refactoring tools to the Flex Builder IDE.

Some themes that have been mentioned by Adobe and have been incorporated into Flex 4 are as follows: Flash Builder is available in two versions: Standard and Premium,[15] the premium adds the following features; May 3, 2011, Adobe shipped Flash Builder 4.5 copying Flex 4.5 (SDK only) which delivers full support for building Flex and ActionScript applications for Google Android, as well as support for building ActionScript applications for BlackBerry Tablet OS and Apple iOS.

Concurrent with pre-release of BlazeDS, Adobe is publishing the AMF binary data protocol specification, on which the BlazeDS remoting implementation is based, and is attempting to partner with the community to make this protocol available for major server platforms.