SWF file format specification

The SWF file format (pronounced “swiff ”) delivers vector graphics, text, video, and soundover the Internet and is supported by Adobe® Flash® Player software.

The SWF file format isdesigned to be an efficient delivery format, not a format for exchanging graphics betweengraphics editors.

It is designed to meet the following goals:

On-screen display—The format is primarily intended for on-screen display and supportsanti-aliasing, fast rendering to a bitmap of any color format, animation, and interactivebuttons.

Extensibility—The format is a tagged format, so it can be evolved with new features whilemaintaining backward compatibility with earlier versions of Flash Player.

Network delivery—The format can travel over a network with limited and unpredictable bandwidth. The files are compressed to be small and support incremental rendering throughstreaming. The SWF file format is a binary format and is not human readable like HTML. The SWF file format uses techniques such as bit-packing and structures with optional fieldsto minimize file size.

Simplicity—The format is simple so that Flash Player is small and easily ported. Also, FlashPlayer depends upon a limited set of operating system features only.

File independence—The files display without dependence on external resources suchas fonts.

Scalability—The files work well on limited hardware, and can take advantage of betterhardware when it is available. This ability is important because computers have differentmonitor resolutions and bit depths.

Speed—The files render with quick, high quality.

Scriptability—The format includes tags that provide sequences of byte codes to beinterpreted by a stack machine. The byte codes support the ActionScript™ language. FlashPlayer provides a runtime ActionScript object model that allows interaction with drawingprimitives, servers, and features of Flash Player.

SWF files have the extension .swf and a MIME type of application/x-shockwave-flash.

The SWF format has evolved through several versions. Through SWF 5, substantial additionswere made to the SWF tag set. Starting with SWF 6 and later, the SWF format changes less,as more new features are implemented partly or entirely at the ActionScript level. Startingwith SWF 9, the ActionScript 3.0 language, which employs the new ActionScript VirtualMachine 2 (AVM2) can be used. Anyone planning to generate SWF file content that usesnewer features should become familiar with the ActionScript object model that Flash Playerexposes. Some references for this information are Programming ActionScript 3.0 (seelivedocs.adobe.com/flex/2/docs/wwhelp/wwhimpl/js/html/wwhelp.htm?href=Part5_ProgAS.html), ActionScript 3.0 Language Reference (seelivedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/), and the Adobe ActionScript VirtualMachine 2 (AVM2) Overview at www.adobe.com/go/avm2overview/ (PDF file).Adobe seriously considers all feedback to the SWF file format specification. E-mail anyunclear or potentially erroneous information within the specification to Adobe atflashformat@adobe.com. All such email submissions shall be subject to the Submitt