Flasm is a Flash bytecode assembler .

It assembles your entire SWF including all the timelines and events. Looking at disassembly, you learn how the Flash compiler works, which improves your ActionScript skills. You can also do some optimizations on the disassembled code by hand or adjust the code as you wish. It then applies your changes to the original SWF, replacing original actions.

It’s also possible to embed Flasm actions in your ActionScript, making optimizing of large projects more comfortable.

It is not a decompiler. What you get is the human readable representation of SWF bytecodes, not ActionScript source. If you’re looking for a decompiler, Flare may suit your needs. However, Flare can’t alter the SWF.



flasm [command] filename


   -d     Disassemble SWF file to the console
   -a     Assemble Flasm project (FLM)
   -u     Update SWF file, replace Flasm macros
   -b     Assemble actions to __bytecode__ instruction or byte sequence
   -z     Compress SWF with zLib
   -x     Decompress SWF


cyborg@cyborg:~$ flasm -d file.swf 
movie 'file.swf' compressed // flash 10, total frames: 1, frame rate: 30 fps, 800x600 px
  fileAttributes attrUseNetwork,attrActionScript3,attrHasMetadata
  metadata '<rdf:RDF xmlns:rdf=\'http://www.w3.org/1999/02/22-rdf-syntax-ns#\'><rdf:Description rdf:about=\'\' xmlns:dc=\'http://purl.org/dc/elements/1.1\'><dc:format>application/x-shockwave-flash</dc:format><dc:title>Adobe Flex 4 Application</dc:title><dc:description>http://www.adobe.com/products/flex</dc:description><dc:publisher>unknown</dc:publisher><dc:creator>unknown</dc:creator><dc:language>EN</dc:language><dc:date>Jul 22, 2015</dc:date></rdf:Description></rdf:RDF>'
  scriptLimits recursion 1000 timeout 60
  // unknown tag 87 length 1000

  defineMovieClip 2 // total frames: 0
  end // of defineMovieClip 2
  // unknown tag 82 length 72599
  // unknown tag 76 length 67

cyborg@cyborg:~$ flasm -x file.swf 
file.swf successfully decompressed, 74234 bytes


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