Regular groups versus movie clip groups

Macromedia Flash (the authoring tool and SWF format) doesn't have the LiveMotion concept of groups as containers that can be animated and transformed like other objects. Therefore, LiveMotion breaks apart any groups in your animations when it exports them, writing transformation information for each item in the group. One exception to this is movie clip groups, which LiveMotion exports as SWF native movie clips. By giving each member of a group only the transformations unique to it, and by applying the shared transformations at the movie clip group level, you can avoid significantly increasing the file size. The more frames, objects, and attributes you use, the more the file-size savings increase.

You can greatly reduce file size by duplicating groups and making them movie clip groups. When exporting such groups, LiveMotion wraps their contents in a Macromedia Flash movie clip. If the contents and transformations are identical, the Flash player recognizes that they're the same and reuses the contents.

Using movie clip groups is recommended if you're making a linear animation. Remember, though, that if you stop the main timeline, movie clip groups continue to play unless you add a behavior that targets and stops them. For more information, see Creating movie clip groups.