|This article is incomplete.
An unlockable stage is a stage in the Super Smash Flash series that is not available at the start of the game (unlike a starter stage), but must be unlocked. Like an unlockable character, it is required to accomplish a particular in-game feat and once completed, a notice will be shown, telling the player that the stage has been unlocked.
List of unlockable stages
|Battlefield||Super Smash Bros.||Clear All-Star with any character.|
|Final Destination||Super Smash Bros.||Unlock all characters.|
|Devil's Machine||EarthBound||Select Ness' ninth costume and self-destruct three times on a Group match.|
|Final Valley||Naruto||Clear event #12: Shadow Clone Showdown.|
|Hyrule Castle||The Legend of Zelda||Complete Classic with Link, Zelda, or Sheik on Normal difficulty or higher without using any continues.|
|Metal Cavern||Super Smash Bros.||Complete Classic on Hard difficulty or higher with any character, without using any continues.|
|Mushroom Kingdom||Mario||Complete Classic for the first time.|
|Saffron City||Pokémon||Complete Classic with Jigglypuff.|
|Steel Diver||Steel Diver||With any character, self-destruct in the bottom blast line on Gangplank Galleon, Lake of Rage, or Planet Namek 20 times total.|
|Waiting Room||Super Smash Bros.||Play any Group match with Sandbag participating.|
|World Tournament||Dragon Ball||Play 15 Group matches.|
In demo versions
These stages were made unlockable when first introduced in their respective demo versions:
|Chaos Shrine||FINAL FANTASY||Unlock Black Mage.||0.7|
|Clock Town||The Legend of Zelda||Accumulate a total of less than 5 minutes with all starter characters in Target Smash.||0.8|
|Sand Ocean||F-Zero||Play 10 Group matches with Captain Falcon.|
|Desk||Chibi-Robo!||Clear event #26: Cleaning Duty.||Beta 1.0.0|
- ↑ Only in Beta 1.0.0. Has been a starter since Beta 1.0.1.