flex.apache.org

To start developing with Apache Flex, you need three things: the Flex SDK, an ActionScript 3 (AS3) coding environment, and an IDE that supports MXML and AS3. Apache Flex uses MXML for layout and AS3—an ECMAScript-based language similar to JavaScript—for coding, and the project points developers to Eclipse-based IDEs such as Adobe Flash Builder and FDT. Before committing, note one important constraint from the official site: Flash Player in the browser is no longer supported by Adobe and the major browser vendors after the end of 2020, so browser-targeted work should be planned around Apache Royale instead, while mobile and desktop output through the Adobe AIR runtime provided by Harman remains supported.

The Core Components

1. The Flex SDK

The SDK is the foundation. The Apache Flex download page lists several options depending on your role:

If you are building applications rather than modifying the framework itself, the Installer is the entry point the project designates for you. Source code and binaries are aimed at people working on the SDK.

2. A Coding Setup: MXML and AS3

Flex separates layout from logic: MXML describes the interface, and AS3 handles behavior. You do not need a separate compiler toolchain beyond the SDK, but you do need an editor or IDE that understands both file types.

3. An IDE

The site names Eclipse-based IDEs—Adobe Flash Builder and FDT—as the tooling to use. The stated advantage is that you can "utilize the tools you are already familiar with," so if you already work in an Eclipse environment, the transition is short.

Learning Resources to Use First

The documentation section of the site organizes material you can work through in this order:

• Getting Started — the natural first stop for setup and a first project.
• Using Flex — usage guidance beyond the basics.
• Videos — visual walkthroughs.
• Flex ASDocs — API reference for the framework classes.
• Developer FAQ — answers to common development questions.
• FlexUnit Tutorials and FlexUnit ASDocs — for unit testing your code.
• Tour de Flex — a showcase of components and techniques, also available as source code.

For community help, the project lists Mailing Lists, a Third-Party Wiki, a Blog, and a Bug Tracker.

Decide Your Target Before You Install

The platform you intend to ship to changes what "getting started" means:

• Browser output — Flash Player browser support has ended. The project explicitly directs browser-targeted work to Apache Royale, its sister project, which lets you keep using ActionScript while outputting native JavaScript and HTML.
• Desktop applications — built on the Adobe AIR runtime provided by Harman, which the site states is still supported.
• Mobile applications — also via Adobe AIR, targeting iOS devices (iPod, iPhone, iPad), Android smartphones and tablets, and BlackBerry Playbook.

So the practical sequence is: confirm your deployment target is AIR-based (desktop or mobile) or plan a Royale migration for browser work; then download the Flex SDK Installer; then set up an Eclipse-based IDE; then work through Getting Started and the ASDocs.

Licensing and Support Context

Apache Flex is completely open source, released under the Apache License, version 2.0, which the project notes is compatible with business needs. It is backed by the Apache Community for updates, support, and help—relevant if you are evaluating whether the framework fits a long-lived project. The site also maintains a Flex Showcase of desktop and mobile applications built with Flex, and you can submit your own application for inclusion.

Apache Flex is an open-source framework for building expressive web and mobile applications, released under the Apache License 2.0 and backed by the Apache community. It uses MXML for layout and ActionScript 3 (AS3) for coding, and targets browsers via Adobe Flash Player and JavaScript, desktop via Adobe AIR, and mobile platforms including iOS and Android. The most important condition to understand before adopting it: Adobe and the major browser vendors ended Flash Player support in the browser at the end of 2020, so Flex is no longer a path to browser-delivered content — for that, the project points to its sister project Apache Royale, which lets you keep using ActionScript while outputting native JavaScript and HTML.

What Flex is made of

Tooling follows familiar patterns: Eclipse-based IDEs such as Adobe Flash Builder and FDT are listed among the options, so developers already working in that ecosystem can reuse existing tools.

What you can still build with it

According to the project, Flex output to mobile and desktop platforms through the Adobe AIR runtime provided by Harman remains supported. That makes the practical target set:

• Desktop applications packaged with Adobe AIR.
• Cross-platform mobile applications for iOS devices (iPod, iPhone, iPad), Android smartphones and tablets, and BlackBerry Playbook.
• Browser content — only via the legacy Flash Player path, which the project itself flags as ending; use Apache Royale instead if browser output is the goal.

Who should choose it, and who should not

Flex fits if you maintain an existing Flex codebase, need to ship or sustain an AIR-based desktop or mobile app, or want a single MXML/AS3 skill set across those targets.

Flex does not fit if your requirement is new browser-delivered content. The project's own guidance is to evaluate Apache Royale for that case, since it preserves ActionScript while producing native JavaScript and HTML.

Getting started

The download page lists several entry points depending on your role:

• Application developers: Flex SDK Installer, or FlexJS "beta".
• SDK developers: SDK source code and SDK binaries.
• Companion tools: FlexUnit (with tutorials and ASDocs), BlazeDS source code, Tour de Flex source code, Squiggly spell checker, and Flex utilities.

Documentation is organized under Getting Started, Using Flex, Videos, Flex ASDocs, and an older documentation reference, with a Developer FAQ and mailing lists for community support. Previous versions are also available if you need to match an existing project's SDK level.

A reasonable first check: confirm your target runtime (AIR desktop/mobile versus browser), then pick the matching download and follow Getting Started before committing to a migration or new build.

The official Apache Flex site (flex.apache.org) is the starting point for both downloads and community participation. From its Download section you can get the Flex SDK Installer, SDK source code, SDK binaries, the FlexJS beta, FlexUnit, BlazeDS source, Tour De Flex source, Squiggly spell checker, and Flex utilities, plus previous versions. The Community section links to mailing lists, the blog, the Flex Showcase, and a third-party wiki, while Development links to source code, the bug tracker, the developer FAQ, and documentation.

Downloading Apache Flex

The download page groups files by audience, which helps you pick the right one:

If you just want to build an app, start with the Flex SDK Installer. If you plan to modify or extend the framework, take the SDK Source Code or SDK Binaries instead.

Community Channels

The site's Community section points to:

• Mailing Lists — the primary support and discussion channel
• Blog — project news and updates
• Flex Showcase — desktop and mobile apps built with Flex; you can submit a request to have your own app listed
• Third-Party Wiki — community-maintained material
• How to get involved — guidance for contributing

For development-specific questions, the Developer FAQ and Documentation (Getting Started, Using Flex, Videos, Flex ASDocs, FlexUnit Tutorials, FlexUnit ASDocs) sit under Development alongside the Source Code and Bug-Tracker.

One Important Constraint Before You Download

The site carries a clear notice: Flash Player in the browser is ending — Adobe and the major browser vendors (Google Chrome, Mozilla Firefox, Microsoft Edge) announced they would stop supporting the Flash Player runtime at the end of 2020. If your goal is browser output, the project directs you to its sister project Apache Royale, which lets you keep using ActionScript while outputting native JavaScript and HTML.

Flex output to mobile and desktop through the Adobe AIR runtime (provided by Harman) is still supported, so AIR-targeted work remains a valid path.

Licensing and Tooling Notes

Apache Flex is released under the Apache License, version 2.0, and is backed by the Apache Community for updates and support. Development uses MXML for layout and AS3 for coding, with Eclipse-based IDEs such as Adobe Flash Builder and FDT among the tooling options mentioned on the site.

Practical Next Steps

1. Decide your target: browser (consider Apache Royale instead), or desktop/mobile via Adobe AIR.
2. Go to the Download section and choose the Flex SDK Installer for app development, or SDK source/binaries if you're working on the SDK.
3. Join the Mailing Lists for support, and bookmark the Developer FAQ, ASDocs, and Bug-Tracker for ongoing work.
4. Check the Flex Showcase for examples of what others have built, and submit your own app if you want it listed.

Apache Flex applications can target browsers, desktops, and mobile devices, but the browser path has a hard constraint: Adobe Flash Player support in browsers ended at the end of 2020, and Adobe along with Google Chrome, Mozilla Firefox, and Microsoft Edge announced they would no longer support the Flash Player runtime. If you need to output content to the browser today, the Apache Flex site points to its sister project, Apache Royale, which lets you keep using ActionScript while outputting native JavaScript and HTML. Desktop and mobile output through the Adobe AIR runtime provided by Harman is still supported.

Platform Targets at a Glance

Browser

The original Flex value proposition was building expressive web applications that run in all browsers via Flash Player, with JavaScript also part of the described approach. That path is effectively closed for new browser-facing work because the major browser vendors dropped the Flash Player runtime. The site's own guidance is to check out Apache Royale if browser output is the goal.

Desktop

Flex desktop applications rely on the Adobe Integrated Runtime (Adobe AIR). The site states that Flex output to desktop platforms through the Harman-provided AIR runtime is still supported, so desktop remains a viable target.

Mobile

Flex supports cross-platform mobile applications through Adobe AIR, with the site naming Apple iPods, iPhones, iPads, Android-based smartphones and tablets, and BlackBerry Playbook devices as targets. As with desktop, this depends on the AIR runtime rather than the browser Flash plugin.

What This Means for Choosing a Target

• If you need browser delivery: plan on Apache Royale rather than the Flash Player path, since browser Flash support has ended.
• If you need desktop or mobile apps: Apache Flex with Adobe AIR remains an option the project describes as supported.
• If you are maintaining an existing Flex app: the platform decision hinges on where it runs — AIR-based desktop and mobile deployments are unaffected by the browser plugin shutdown, while browser deployments need a migration path.

Practical Check Before You Commit

Confirm the runtime your deployment actually uses. A Flex application packaged for Adobe AIR is a different delivery mechanism from one that expected a browser Flash plugin, and only the latter is affected by the end of browser Flash Player support. The Apache Flex download page lists the Flex SDK Installer for application developers, SDK source and binaries for SDK developers, FlexJS beta, FlexUnit, Blaze DS source, Tour De Flex source, Squiggly Spell Checker, and Flex Utilities, plus previous versions — useful if you are setting up a toolchain for a specific target.

Flex itself is open-source under the Apache License, version 2.0, and is backed by the Apache Community for updates and support, so licensing is not a barrier to targeting any of these platforms.

Apache Flex remains usable, but not for browser-based Flash content. The project's own site states that Adobe and all major browser vendors ended support for the Adobe Flash Player runtime at the end of 2020, and directs anyone who needs to output content to the browser toward the sister project Apache Royale, which lets you keep ActionScript while producing native JavaScript and HTML. Flex output to mobile and desktop platforms through the Adobe AIR runtime, provided by Harman, is still supported.

What changed, and what still works

The key distinction is the target platform, not the framework itself:

The site also notes that Flex applications have historically targeted "all browsers by leveraging the Adobe Flash Player and JavaScript," and that mobile targets included iOS devices, Android phones and tablets, and BlackBerry Playbook. The browser leg of that list is the part affected by the Flash Player shutdown.

Why the framework itself is not the problem

Apache Flex is an open-source framework released under the Apache License 2.0, backed by the Apache community for updates and support. Nothing about the license or the project's governance changed with the end of Flash Player. What changed is the runtime that browser-delivered Flex content depended on. That is why the site's guidance is about redirecting browser output to Royale rather than about Flex being discontinued.

Flex uses MXML for layout and ActionScript 3 (an ECMAScript-based language) for coding, and the site points to Eclipse-based IDEs such as Adobe Flash Builder and FDT, or the command-line compiler, as tooling. Those development workflows are unaffected by the browser runtime question.

Deciding what to do with an existing Flex application

The decision hinges on where your application runs today:

• Browser-delivered Flash content: Plan a migration. The site's recommended route is Apache Royale, which preserves ActionScript skills while outputting native JavaScript and HTML. Treat this as a rewrite of the delivery layer, not a recompile.
• Desktop application on Adobe AIR: You can keep it running and maintained, since AIR support continues through Harman. Confirm your AIR runtime distribution and update path with Harman as part of normal maintenance.
• Mobile application on Adobe AIR: Same as desktop — supported, with the same caveat about sourcing the AIR runtime from Harman.
• Mixed codebase: Separate the shared business logic from the presentation layer. The ActionScript logic is the part most likely to carry over to Royale, while Flash-dependent UI and browser integration will need rework.

Practical next steps

1. Inventory where each application actually executes — browser plugin, AIR desktop, or AIR mobile. The site's own framing makes this the deciding factor.
2. For browser targets, review Apache Royale's documentation and getting-started material before committing to a migration plan; the site positions it explicitly as the path for continuing to use ActionScript with JavaScript/HTML output.
3. For AIR targets, verify your current runtime version and support arrangements with Harman, since AIR is provided by them rather than by Adobe.
4. Check the Flex project's download and documentation pages for current SDK, FlexJS (marked beta on the site), and FlexUnit materials if you are maintaining or starting development.

The short answer for planning purposes: Flex is alive as a framework, AIR-delivered desktop and mobile apps remain supported, and browser output needs to move to Apache Royale.