Elite Smash is an unlockable online mode on Quickplay that allows people with a certain Global Smash Power to access. Once a character reaches the necessary GSP, that character is allowed to fight in Elite Smash. However, if the character's GSP goes below the threshold, they will no longer be allowed to fight. Characters in Elite Smash will be highlighted on the character select screen, while characters not in Elite Smash can still be played, but will be played in the usual Quickplay instead of Elite Smash.
Elite Smash was first revealed in the November 1st, 2018 Smash Bros Direct. In the same direct, Masahiro Sakurai noted that developers would be looking at fights in Elite Smash to determine how to balance characters.
The number of GSP required to access Elite Smash is not set, but rather it increases as more people reach the threshold. The win ratio the player has playing as a certain fighter also influences whether or not Elite Smash can be played as said character.
Players will be notified when they unlock Elite Smash. The Quickplay and Background Matchmaking options will have an "Elite" tag on the top right corner.
Battling in an Elite Smash match for the first time will give the player a notice about it.