.FLA File Format

Flash and Animate document

Introduction

An .fla file is the editable document of a Flash animation, game or application. It holds the stage, the timelines with their layers and frames, the vector shapes, the library of symbols, the imported bitmaps and sounds, and the ActionScript written on frames and buttons. It is the source, not the program: publishing it makes a .swf file, which Flash Player, Adobe AIR or an emulator such as Ruffle runs. Only the authoring tool opens the .fla itself.

The format belongs to the authoring tool that began as FutureSplash Animator in 1996. Macromedia bought it at the end of that year and called it Macromedia Flash. Adobe bought Macromedia in 2005, sold the tool as Adobe Flash Professional, and renamed it Adobe Animate in February 2016. Animate 2024 is the latest release. Since February 2026 Adobe keeps it in maintenance mode, with security and bug fixes but no new features.

Over those thirty years the .fla has been three formats. Versions that only add to a format share it; a version that changes what is already there is a separate format. Flash MX 2004 changed every string in the document from single bytes to UTF-16, and Flash CS5 replaced the binary compound file with a ZIP archive of XML. The releases in between raised the revision numbers of single records and added fields at their ends, which a reader handles by testing each record’s revision, so they stay in one format.

An .fla file dropped on any page opens in the explorer. It lists the streams of a binary FLA or the members of an XFL archive, shows the bitmaps, and pulls out every ActionScript script in the document, each labelled with its timeline, layer and frame, or with the button or movie clip it belongs to.

Variations

FormatVariationAboutOpen
.FLAFlash MX and earlier document (binary FLA, single-byte text)Microsoft compound file of Flash’s own MFC object streams, every string in single bytes.Open
.FLAFlash MX 2004 to CS4 document (binary FLA, UTF-16 text)The same compound file with UTF-16LE strings and stream names, from Flash MX 2004.Open
.FLAXFL document (Flash CS5 and later, ZIP)A ZIP archive of XML (DOMDocument.xml, LIBRARY/) and binary assets (bin/), from Flash CS5.Open

Flash MX and earlier document (binary FLA, single-byte text)

The documents of FutureSplash Animator and Macromedia Flash 1 to Flash MX, from 1996 to 2002. The file is a Microsoft compound file, a small file system of sectors inside one file. It holds a Contents stream for the document as a whole and one stream for each scene, each symbol and each imported bitmap or sound. Each stream is a tree of Flash’s own objects, written with the MFC library of the Windows program. Every string is in single bytes, in the Windows code page of whoever saved it.

The file starts with the compound file signature D0 CF 11 E0 A1 B1 1A E1. The root entry’s class ID is {597CAA70-72AA-11CF-831E-524153480000}, or else the root holds a Contents stream and Page or Symbol streams. The first byte of Contents is 0x29 or lower.

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

The documents of Flash MX 2004, Flash 8, Flash CS3 and Flash CS4, from 2003 to 2008, and of the “Save as CS4” option in later releases. The container and the streams are the same, but every string is UTF-16LE. Script text, layer names and labels carry an FF FE FF marker that says so, but the stream names listed in Contents carry none, so a reader made for the older format misreads them. Flash CS4 also names its streams with a time stamp, such as P 1 1227523356.

The file starts with D0 CF 11 E0 A1 B1 1A E1 and has Flash’s class ID or its streams, as above. The first byte of Contents is 0x38 or higher.

XFL document (Flash CS5 and later, ZIP)

The documents of Flash Professional CS5, from 2010, and of every release since, up to Adobe Animate. The .fla is a ZIP archive. DOMDocument.xml describes the document and its scenes, LIBRARY/ holds one XML file for each symbol and the files that were imported, bin/ holds bitmaps in Flash’s own form, and PublishSettings.xml the publish settings. The same files can also be kept unzipped in a folder, opened through an .xfl file.

The file starts with 50 4B 03 04, a ZIP local file header, and holds a member named DOMDocument.xml whose root element is <DOMDocument>. Most also hold a mimetype member, application/vnd.adobe.xfl, but it is not always first, so it does not decide.

Telling them apart

The explorer checks the container first, then what only a Flash document has:

  1. A file that starts D0 CF 11 E0 A1 B1 1A E1 is a compound file. It is a binary FLA if its root entry has Flash’s class ID, or if the root holds a Contents stream and at least one timeline stream (Page 1, Symbol 1, or Flash CS4’s P 1 … and S 1 …). Word, Excel and Windows Installer files are compound files too, and have neither.
  2. In a binary FLA, the first byte of the Contents stream is the document revision, which names the release that saved it (table below). Up to 0x29 the text is single-byte; from 0x38 it is UTF-16. For a value not in the table, the encoding of the stream names in Contents decides.
  3. A file that starts 50 4B 03 04 is an XFL document if its central directory lists DOMDocument.xml and that file’s root element is <DOMDocument>. An ordinary ZIP, a .docx or a .jar has no such member.
First byte of ContentsSaved byFormat
0x10FutureSplash Animator, Flash 1single-byte text
0x11Flash 2single-byte text
0x14Flash 3single-byte text
0x1BFlash 4single-byte text
0x20Flash 5single-byte text
0x29Flash MXsingle-byte text
0x38Flash MX 2004UTF-16 text
0x3FFlash 8UTF-16 text
0x43Flash CS3UTF-16 text
0x47Flash CS4UTF-16 text

The values for FutureSplash Animator, Flash 1 and Flash 2 come from the JPEXS FLA converter; no file from those releases has been examined for this site.

Versions

Every release of the authoring tool, with the format it saves. The Contents byte is the first byte of a binary FLA’s Contents stream. The last column gives the older formats that Save As offers, where that is known.

ReleaseReleasedVersionContents byteSavesSave as older
FutureSplash AnimatorMay 1996–0x10Binary, single-byte–
Macromedia Flash 1December 199610x10Binary, single-byte–
Macromedia Flash 2199720x11Binary, single-bytenot known
Macromedia Flash 3199830x14Binary, single-bytenot known
Macromedia Flash 4199940x1BBinary, single-bytenot known
Macromedia Flash 5200050x20Binary, single-bytenot known
Macromedia Flash MXMarch 200260x29Binary, single-bytenot known
Macromedia Flash MX 2004September 200370x38Binary, UTF-16Flash MX
Macromedia Flash 8September 200580x3FBinary, UTF-16not known
Adobe Flash CS3 Professional200790x43Binary, UTF-16Flash 8
Adobe Flash CS4 ProfessionalSeptember 2008100x47Binary, UTF-16Flash CS3
Adobe Flash CS5 ProfessionalApril 201011–XFL 2.0Flash CS4 (binary)
Adobe Flash CS5.5 Professional201111.5–XFL 2.1Flash CS5; users report CS4 too
Adobe Flash CS6 Professional201212–XFL 2.2not known
Adobe Flash Professional CCJune 201313–XFL 2.4none
Adobe Flash Professional CC 2014June 201414–XFLnone
Adobe Flash Professional CC 2015June 201515–XFLnone
Adobe Animate CC (renamed)February 201615.1–XFLnone
Adobe Animate CC 2017November 201616–XFLnone
Adobe Animate CC 2018October 201718–XFLnone
Adobe Animate CC 2019October 201819–XFLnone
Adobe Animate 2020November 201920–XFLnone
Adobe Animate 2021October 202021–XFLnone
Adobe Animate 2022October 202122–XFLnone
Adobe Animate 2023October 202223–XFLnone
Adobe Animate 2024October 202324–XFLnone
Adobe Animate 2024, latest updateSeptember 202624.0.15–XFLnone
  • The XFL numbers are the xflVersion attribute of DOMDocument.xml. Later releases write later values, which are not listed because they have not been confirmed.
  • Flash CS5 opens binary FLAs from every earlier release, and so does every release since. Its own .fla is the ZIP form of XFL.
  • In the binary era Save As went back at most two releases, and from Flash CS5.5 one. Flash Professional CC dropped the older formats from Save As altogether.
  • There was no Animate 2025 or 2026. On 2 February 2026 Adobe announced that Animate would stop being sold on 1 March 2026, then reversed the decision two days later: Animate stays available in maintenance mode.
  • The release days of Flash 2 to 5, CS3, CS5.5 and CS6 are not certain, so only the years are given.

ActionScript in FLA

Is it text? Mostly yes, and it is never compiled. A script typed into the Actions panel is kept as the source text exactly as typed, with its comments, tabs and line breaks. Compiling to bytecode happens only when the document is published as a SWF, so an .fla holds no bytecode, except inside compiled clips, which are SWF files themselves. Two kinds of script are not text: the actions of Flash 4 and earlier, and scripts built in normal mode in Flash 5 and Flash MX.

Saved byHow scripts are storedEncoding
FutureSplash Animator, Flash 1 to 4Not text. Actions are commands chosen from menus, kept as records: a kind of action, then its URL, target, frame number and other fields.–
Flash 5 and Flash MX, expert modeActionScript 1.0 source text, in an ActionScript block on the keyframe, button or movie clip.Single bytes in the author’s Windows code page
Flash 5 and Flash MX, normal modeA list of statements with their fields, from which Flash rebuilds the text. Later revisions also keep the displayed text of each statement.Single bytes
Flash MX 2004 to CS4Source text in the same ActionScript block: ActionScript 1.0 and 2.0, and 3.0 from CS3.UTF-16LE
Flash CS5 and later (XFL)Source text in a <script> element, inside <![CDATA[ … ]]>, in DOMDocument.xml for scenes and in the symbol’s XML file in LIBRARY/.UTF-8

Scripts sit on keyframes, and in ActionScript 1.0 and 2.0 also on button and movie clip instances, as on (release) { … } and onClipEvent (enterFrame) { … } handlers. Classes are not kept in the document. An ActionScript 2.0 or 3.0 class lives in its own .as file on the classpath, and the document only names it: as the linkage class of a library symbol, or as the document class in the publish settings. ActionScript 1.0 and 2.0 scripts can also pull in a file with #include "Script.as" when the document is published.

A binary FLA often holds more scripts than it shows. Flash’s ordinary save writes the streams that changed into new sectors and marks the old ones free without clearing them, so earlier versions of scripts survive in free sectors until the file is saved with Save and Compact. The explorer lists them separately, as older copies that are not part of the document.

Links

Software

  • Adobe Animate – Adobe’s animation tool, formerly Flash Professional, which opens every kind of FLA and saves XFL (Windows, macOS)
  • JPEXS Free Flash Decompiler – free SWF decompiler that can export a SWF as an FLA document, binary or XFL (Windows, macOS, Linux)

Developers

  • jpexs-fla-convert – library that reads and writes binary FLA and XFL documents (Java)
  • xfl-schema – an unofficial XML schema for XFL documents, from the JPEXS project (XSD)
  • fla-decoder – reader for binary FLA documents (Python); Kreijstal’s fork adds notes on the format
  • fla-viewer – viewer for XFL documents, and partly for binary ones (TypeScript)
  • xfl2svg – converts the shapes of XFL documents to SVG (Python)

Reference