Universe

A universe is a term first used by the  community to collectively refer to all the particular characters, stages, items, and other properties appearing in the fighting games that are thematically featured in another game franchise.

Major universes
These are the franchises that the  series games classify as major enough that they assign each franchise its own unique series symbol that appears with characters and stages belonging to that franchise. These franchises generally have playable characters, stages, items, and other properties that all appear in the Super Smash Flash games as part of their primary content. However, the minimum requirement for a symbol is to contribute one playable character or one stage to the games.

Supporting universes
These are the various franchises that have not been recognized as primary universes by any Super Smash Flash game, and this is indicated by the fact these franchises do not carry their own series symbols. As a general rule, such universes lack any playable characters or stages in the games, but any of the following franchises contributes an item, Assist Trophy, music, or other minor elements. Like in the original Super Smash Bros. games, the universe may be assigned the property and its respective franchise the Super Smash Bros. series symbol.