Online play, sometimes known as netplay, is the act of playing games in the Super Smash Bros. series with other players via the Internet. Thus far, Super Smash Bros. Brawl, both versions of Super Smash Bros. 4, and Super Smash Bros. Ultimate have had netplay officially supported by Nintendo; while released without native netplay capabilities, modern methods exist for playing both Smash 64 and Melee online.
The Nintendo 64 does not natively support online play, though the idea was explored as part of the 64DD add-on. As such, online play for Smash 64 is accomplished through the use of emulators, such as Project64k. Owing to the lower system requirements of Nintendo 64 emulators and the rather fragmented community surrounding Smash 64, netplay is among the most common ways to play the game in the current scene. Initially, netplay was achieved via servers such as Smash FU and The Galaxy, but the community has since changed to mostly using peer-to-peer connections.
While the Nintendo GameCube does have limited support for internet connectivity with appropriate adapters, Melee was released prior to the official release of these adapters, and as such, it does not natively support online play. Like Smash 64, online play for Melee is generally accomplished through emulators, particularly Dolphin.
Prior to Dolphin featuring netplay functionality, experimental online play was previously performed by a variety of tunneling softwares that could directly connect GameCube consoles to one another, such as via XLink Kai or exploits in Phantasy Star Online for the GameCube. These methods, however, were difficult to set up, required extensive knowledge of the software on hand and networking protocols, and required both players to be using the same version of Melee. Matches themselves often had desyncs, with items notably being implicated.
Online play later experienced mainstream popularity with the GameCube and Wii emulator Dolphin, which allowed for considerably easier connectivity between players, as well as being considerably more reliable in terms of synchronisation. Initially holding only niche popularity due to Dolphin's high system requirements, the gradually increasing power of personal computers and improvements to Dolphin's performance has allowed for more Melee players to partake in online play.
The Nintendo Wii was the first Nintendo home console to support online play, with Nintendo allowing the device to take advantage of the Nintendo Wi-Fi Connection. As a result, Brawl was the first game in the series to officially support online play, allowing players to fight against either strangers or friends. In addition, gameplay mods for Brawl could also be unofficially played online via this protocol, though all players would need the mod in order to prevent desyncs from occurring.
Official support for online play in Brawl was ended on 20 May 2014. A variety of methods, however, still allow for Brawl to be played online; Canadian smasher pidgezero_one developed a method to play Brawl and Brawl gameplay mods via the Wii, and Dolphin also supports online play via the computer.
Like Brawl, both Super Smash Bros. for Wii U and Super Smash Bros. for Nintendo 3DS natively support online play, though this time, the service is provided via the Nintendo Network. The service also offers a variety of benefits over Brawl's online play, particularly in regards to options and matchmaking. The overall concept, however, remains the same, with players being able to play against either strangers or friends via the internet. The latest version of the game must be downloaded to access online modes, as different players going online with different versions would cause compatibility issues and desyncing, if not break the game entirely.
Currently, there are no methods to play Smash 4 online outside of the Nintendo Network; that said, Citra and Cemu, experimental emulators for the 3DS and Wii U respectively, could potentially see online play occur on personal computers like previous games in the series.
Ultimate has native online support much like Brawl and Smash 4. However, this time online play is a paid service as part of Nintendo Switch Online. Rather than selecting from modes with specific rules, players can now choose their own preferred rules and the game will attempt to match players with similar desires. Compared to previous games, Ultimate allows for a wider selection of rules when playing with anyone. Just like Smash 4, the latest version of the game must be downloaded to access the online modes for the same reasons.
As of version 4.0.0, upon opening the Online Submenu, the player is given four options: Smash, Spectate, Shared Content, or Online Tourney. Upon choosing Smash, there are three options to choose from: Quickplay, Battle Arenas, and Background Matchmaking. Quickplay has the player select Solo or Co-op (local), with a Preferred Rules switch underneath the two options. Preferred rules include the format, time limit, stage, stock count, whether Final Smash Meter is on or off, and which items should be turned on. If a player accrues enough Global Smash Power with a single fighter, the player can use that fighter in Elite Smash: a mode similar to Quickplay where players are not matched up with those not in Elite smash. However, the player needs to maintain that GSP count, and will be kicked from Elite smash if they dip below the threshold.
Upon choosing Solo or Co-op, the player(s) can choose their character(s), and are taken to the Online Practice Stage. There they can train with CPU partner(s) while waiting for opponent(s).
If the player(s) choose Background Matchmaking, they can choose Solo or Co-op, their fighters and preferred rules. While waiting for their opponent(s), they can participate in various different modes.
Battle Arenas are a new form of online play for the series, being able to make it visible for all (Public), or for Friends only. Arenas can have a password set, preventing unauthorized players from entering. The type can also be set, for All Skill Levels, Veteran Players, Glorious Smashers, Anything Goes, Playground, amiibo Battle (available after update 3.1.0), Elite Only, and Beginners Only (both available after update 6.0.0).
Many players have opted to use emulation via the yuzu emulator in combination with external video streaming software such as Parsec as a means to play Ultimate online. This has become popular in the wider competitive scene mainly due to the problems faced with the native game's online service, with some top players such as Fatality and Dark Wizzy using this technique to play.