When Creative Cloud was launched in June 2013, we added support for HTML5-based panels in several Adobe products. These new panels open up the world of panel development to a wider range of developers who may be more comfortable working with HTML/JavaScript and CSS. Since June, support for HTML5-based panels has been added to more Adobe products. As of now Photoshop CC, Illustrator CC, Premiere Pro CC and Prelude CC support HTML5-based panels.
A preview of Adobe Extension Builder 3, a new developer tool that supports creating HTML5-based extensions, was launched in June at Adobe Labs. You can download it for free from here: http://labs.adobe.com/technologies/extensionbuilder3/
Starting in the middle of 2014 we will begin removing Flash-based extension support in Creative Cloud products, starting with Photoshop CC. We encourage all developers to start planning and migrating to the new extensibility framework based on HTML5.
HTML5-based panels allow developers to leverage the rich ecosystem of existing JavaScript frameworks and tools when creating their panels. HTML5-based panels share the same technology with web applications, which opens up exciting opportunities for integration with web services.
Check out these videos to see how to build and debug HTML5 Extensions.