Home stage

A home stage is the stage that is most commonly associated with a character, by the game and/or by players. There may be more than one home stage for certain characters in the games. Due to the Flash size limit of the original Super Smash Flash, only eight stages were featured, leaving more of the half of the playable characters without a stage belonging to their "universe". The reboot, Super Smash Flash 2, according to its developers, promises to include at least one stage representation per universe, which may mean that all the playable characters could have a home stage.

In Super Smash Flash
As stated above, more of the half of the character roster was left without a stage for representation in Super Smash Flash. For the few characters who actually got a stage representation, those stages are mainly where matches take place in the Classic and the Adventure. It should be noted that all unlocking matches for characters and the All-Star matches take place on the stage.

In Super Smash Flash 2
✅ For Super Smash Flash 2, it was confirmed that every game universe will have stage representation, and, by extent, every playable character. The only known home stages are those who appear in the current demo or the DOJO!!!. Furthermore, it was confirmed that every playable character will have a particular home stage, with many characters even having more than one home stage.

Trivia

 * Despite there being four stages representing the  series in SSF2, including Battlefield, Final Destination and Metal Cavern, the Waiting Room is the only one attributed to Sandbag due to his role as a practice opponent in online practice stages in both SSF2 and official Super Smash Bros. titles.