.FLA File Format

Flash MX 2004 to CS4 document (binary FLA, UTF-16 text)

Introduction

This is the document format of Macromedia Flash MX 2004 and Flash 8, and of Adobe Flash CS3 and CS4 Professional, from 2003 to 2008: the authoring tool now called Adobe Animate. Later releases still write it when a document is saved as Flash CS4. An .fla file holds the whole editable document: its scenes, layers and keyframes, the vector shapes, the library of symbols, the imported bitmaps and sounds, and the scripts, in ActionScript 1.0 and 2.0 and, from Flash CS3, 3.0. Publishing it makes a .swf file.

The file is a Microsoft compound file, the container of old Word and Excel documents: a small file system of fixed-size sectors holding named streams. Each stream is an archive of Flash’s own objects, written with Microsoft’s MFC library as a tree: a scene holds its layers, a layer its frames, and a frame what is on the stage. Every string is UTF-16LE. Script text, layer names and labels carry a marker that says so; the stream names listed in Contents carry none. Flash CS4 also names its streams with a time stamp.

Macromedia and Adobe never published the format. What is known comes from reading files and from projects that read and write them, chiefly the JPEXS FLA converter; the pages here were checked against real files of Flash MX 2004, 8, CS3 and CS4. The documents of Flash MX and earlier have the same container and records but single-byte text, which makes them a separate format; from Flash CS5 the .fla is a ZIP archive of XML. All the variations are on the FLA page.

An .fla file dropped on any page opens in the explorer, which lists its sectors and streams, shows its bitmaps, and pulls out every script, each labelled with its scene or symbol, layer and frame.

Structure

The file is a compound file: a 512-byte header, then numbered 512-byte sectors. Tables in the sectors chain them into streams, and a directory names the streams. All numbers are little-endian.

  1. 0Header the signature D0 CF 11 E0 A1 B1 1A E1, the sector sizes, where the directory and the tables start, and the first 109 FAT sector numbers512 bytes
  2. 512Sectors numbered from 0, in any order: FAT, directory and mini FAT sectors, and the data of the streams512 bytes each
The parts of the container, in order

The streams

Every stream sits directly in the root of the compound file; Flash uses no storages (folders).

StreamIn Flash CS4Holds
ContentsContentsThe document: the list of scenes, the library, the media records, colours, the frame rate and the publish settings.
Page 1, Page 2 …P 1 1227523356 …The timeline of one scene.
Symbol 1, Symbol 2 …S 12 1299599075 …The timeline of one library symbol: a movie clip, a button or a graphic.
Media 1, Media 2 …M 3 …One imported bitmap or sound.

How a timeline is stored

A Page or Symbol stream is one tree of objects, written depth first. Each object starts with its class and its own revision byte, then its children, then its own fields, so a layer’s name comes after all its frames.

CPicPage              the scene or symbol
  CPicLayer           a layer: its frames first, then its name and settings
    CPicFrame         a keyframe: what is on the stage first, then its duration, label and script
      CPicShape       on the stage in that frame:
      CPicSprite        a movie clip instance, with its handlers and name
      CPicButton        a button instance, with its handlers and name
      CPicText          a text field
  CPicLayer           the next layer
    …
The object tree of a timeline stream. See MFC object archive and Pages, layers and frames.

Reference pages

Telling it apart

The explorer’s parser for this format checks three things, in order:

  1. A compound file header that reads: the signature D0 CF 11 E0 A1 B1 1A E1, version 3 or 4 with the matching sector shift, a mini sector shift of 6 and a mini stream cutoff of 4,096, then a FAT, a directory and a root entry that can be followed.
  2. A Flash document: the root entry’s class ID is {597CAA70-72AA-11CF-831E-524153480000}, or the root holds a Contents stream and at least one timeline stream, Page or Symbol, or Flash CS4’s P n stamp and S n stamp. Word, Excel, Windows Installer and other compound files have neither and are turned down.
  3. UTF-16 text: the first byte of the Contents stream, the document revision, is one of this format’s, 0x38 (Flash MX 2004) or higher. A file whose revision is 0x29 or lower belongs to the Flash MX and earlier format. For a revision in neither list, the encoding of the stream names in Contents decides, then the layer names and scripts.

The explorer tries this parser before the single-byte one. Flash CS4 documents saved again by Flash CS5.5 can have a zero or a different class ID on the root; the second test still accepts them, as it does files written by SWF-to-FLA decompilers.

Variants

Links

Software

  • Adobe Animate – Adobe’s animation tool, formerly Flash Professional, which still opens these documents and saves them as XFL (Windows, macOS)
  • JPEXS Free Flash Decompiler – free SWF decompiler that can export a SWF as a binary FLA of this era (Windows, macOS, Linux)

Developers

  • jpexs-fla-convert – library that reads and writes binary FLA documents of every release (Java)
  • fla-decoder – reader for binary FLA documents (Python); Kreijstal’s fork adds notes on the format
  • fla-viewer – viewer for XFL documents that also reads some binary ones (TypeScript)

Reference