.FLA File Format

Introduction

This is the document format of Adobe Flash Professional CS5, from 2010, and of every release since, up to Adobe Animate. 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. Publishing it makes a .swf file, or with Animate’s other document types an HTML5 canvas or WebGL page.

The file is a ZIP archive. Its main member, DOMDocument.xml, describes the document and the timeline of each scene. The LIBRARY/ folder holds one XML file for each symbol, beside the files that were imported, and bin/ holds bitmaps in Flash’s own binary form and compiled clips. The XML is called XFL. Earlier releases saved a binary compound file instead, with single-byte or UTF-16 text; those are separate formats, and all the variations are on the FLA page.

Adobe never published a specification of XFL. What is known comes from reading the files, which are mostly plain XML, and from projects that read and write them, such as the JPEXS decompiler, its unofficial XML schema, and xfl2svg for the shapes. Each release added attributes and elements to the same XML, so every XFL document is one format here.

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

Structure

An XFL document is an ordinary ZIP archive. Members follow one another, each with a local file header, then the central directory lists them all, and the end record says where the central directory is. All numbers are little-endian.

DOMTimeline                 a scene or a symbol’s timeline
  layers
    DOMLayer                a layer: name, colour, type
      frames
        DOMFrame            a keyframe: index, duration, label, tween
          Actionscript      the frame script, as text
          elements          what is on the stage in that frame:
            DOMShape          a shape: fills, strokes and edges
            DOMSymbolInstance an instance of a library symbol
            DOMBitmapInstance a bitmap
            DOMStaticText     a text field

Reference pages

• The ZIP container – local headers, central directory, end record, and the oddities seen in XFL archives
• Files in an XFL document – every member and folder, and what it holds
• DOMDocument.xml – the root element’s attributes and its lists of folders, media, symbols and timelines
• Timelines, layers and frames – the timeline elements, frame numbering, elements on the stage and tweens
• Shapes and edge encoding – fills, strokes and the compact edges string
• The library – symbol, bitmap, sound and other items, and ActionScript linkage
• Bitmaps in bin/ – JPEG and lossless bitmaps in Flash’s own form
• Publish settings – PublishSettings.xml’s profiles and Flash properties
• ActionScript in FLA – frame and instance scripts, classes, the document class and includes
• Versions – the xflVersion of each release

The uncompressed form

Flash CS5 and later can also save a document uncompressed. The result is a folder holding the same members as files and folders: DOMDocument.xml, LIBRARY/, bin/, META-INF/, PublishSettings.xml, and a small file named after the document with the extension .xfl, whose content is the nine bytes PROXY-CS5. Flash opens the document through that file. The same .xfl marker is also found inside the ZIP form.

The unzipped form suits version control, since each symbol is a separate text file. The explorer opens single files only, so it cannot open the folder; zipping the folder’s contents gives an archive the explorer can read.

Telling it apart

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

1. The file starts with 50 4B 03 04, a ZIP local file header.
2. An end of central directory record (50 4B 05 06) is found at the end of the file, and the central directory it points to can be read, record by record. ZIP64 archives are turned down; XFL documents are never that large.
3. The central directory lists a member named DOMDocument.xml, and once inflated its root element is <DOMDocument>.

An ordinary ZIP archive, or another ZIP-based format such as a .docx, .jar, .epub or .idml, has no DOMDocument.xml and is turned down. The mimetype member is not required: in the files seen it comes first in some and last in others, so it is not a fixed signature as it is in EPUB.

Variants

• Flash MX and earlier document (binary FLA, single-byte text) – a compound file of Flash’s object streams, every string in single bytes (FutureSplash Animator to Flash MX)
• Flash MX 2004 to CS4 document (binary FLA, UTF-16 text) – the same compound file with UTF-16LE strings and stream names (Flash MX 2004 to Flash CS4)
• XFL document (Flash CS5 and later, ZIP) – a ZIP archive of XML files and binary assets (Flash CS5 to Adobe Animate)

Links