Tournament rulesets (SSBU)
Tournament legal describes the rules and settings that are generally accepted for use in competitive Smash tournaments. In SSBU, while many elements of tournament rulesets are consistent across major tournaments, they are not set in stone. Some specific details vary from tournament to tournament, with some local tournaments having completely different rulesets depending on the goals of said tournament.
Since the competitive scene is still rather young, and because of the number of stages and the option to turn off stage hazards, there is no set stage list. When the losing player is choosing a counterpick stage, the winning player is allowed to ban two stages they have not counterpicked to or won on in the set. The list compiled below is an estimate based off of tournaments up to Ultimate Nimbus. While Small Battlefield has not seen much tournament play due to the lack of offline tournaments since its introduction, the stage is considered legal at the moment and may be used as a substitute for either Pokémon Stadium. The legality of Minecraft World is debated, due to the ability to chose specific forms, however the lack of offline tournaments since its introduction have inhibited the discussion to a degree. Northern Cave is another recently released stage that has been considered as a potential replacement to Kalos Pokémon League.
The following five stages are on the starter lists of virtually all tournaments:
Common starters/Universal counterpicks
Uncommon starters/Common counterpicks
The following stages rarely see use in larger tournaments, but may still be found in smaller tournaments and tournaments hosted by Nintendo. These stages may also see use in competitive play via the Gentleman's Rule.
Battlefield and Ω forms
Most Battlefield and Ω forms are typically allowed, but there are several that are explicitly banned for one reason or another. Stages that only have two dimensions cause significant differences during gameplay due to manipulating the Z-axis, and as such are always banned. Stages that conceal the ground are banned due to the unfair advantage they provide to characters that lay traps on the stage, such as Snake, Isabelle and Steve.
Stages that manipulate the Z-axis
Stages that conceal the ground
No longer banned as of version 8.0.0