Key difference: FLV and FLA are two types of file format used in Adobe Flash. FLV is a container file format that is used to deliver video over the Internet, whereas the FLA is the work in progress or the source file for the finished SWF file.

FLV and FLA are two types of file format used in Adobe Flash. FLV is a container file format that is used to deliver video over the Internet, whereas the FLA is the work in progress or the source file for the finished SWF file.

FLV stands for Flash Video. There are two main file formats for Flash Video, FLV and F4V. FLV is usually used to deliver video on the internet. The file formats are supported in Adobe Flash Player. They were originally developed by Macromedia, and are currently under Adobe Systems.

FLV is a container file format, similar to .avi or .mov.  A container file specifies how the data streams inside it are organized. The actual organization and representation of the data streams are done by the various types of codecs.

Most websites, including YouTube, Google Video, Hulu, VEVO, Yahoo! Video, MySpace TV, etc., showcase videos in the .flv format. However, similar to AVI and MOV, FLV is a file format, which means that it needs a player to be played. Still, a lot of the players are not capable of playing a FLV file. If one wants to play a FLV file on a website, the file must first be embedded into a player. Hence, the audio and video data within FLV files are encoded in a SWF file. An SWF file can then be embedded directly on to a website.

The SWF file is the file that contains the frame and player controls that one can interacts with on the website. While, FLV is the video that is being played.  Hence, it can be said that FLV is the video, while, SWF is the player.

FLA files, on the other hand, contain the source material for the Flash application. These files can be edited using various types Flash authoring software. FLA files use graphic design, vector graphics and other production tools to create the flash product. These are usually the Flash games or any Flash interactive video. Once the editing on the .fla files is completed, the files are saved in the .swf format. The SWF files are the completed, compiled and published Flash files. This format can then be published to the Internet, submitted to the company it was designed for or shared by the creators with others.

If there are any changes that need to be made to the finished Flash file or if the SWF file needs to be revised, then the designer needs the FLA file. Changes can only be made in the FLA file, and then can be saved again as the SWF file, which can then be republished. There are a number of software currently available, which can be used to get a FLA file from a SWF, whose original FLA file is not available. However, the derived FLA files are never as good as the original.

Comparing FLV and FLA, FLV files tend to be smaller in size than FLA. This is mainly because FLV is simply limited to audio and video, as it is meant for video streaming. Also, this file can be too big, as it would take forever to load on a website.

FLA, on the other hand, is bigger because it needs to retain all the associated resources and data required for the Flash. This amount can be huge as FLA files are used to design animations, interactive menus, and even online games. Hence, a single FLA file can contain video, audio, images, scripting, etc. 

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