In Brawl, once a match ends, players can press the Z button (on a lone Wii Remote, the B button is used instead) to save the replay onto the Wii or an SD card. Replays can only be saved if the match lasted less than 3 minutes, Sudden Death included, despite the game being capable of handling saving much longer matches than this. Hacks that remove this time limit exist for Brawl, and many mods for the game include such a hack; even with this hack, however, replays over 10 minutes do not function properly, as replays stop saving inputs beyond the 10 minute mark. Super Smash Bros. 4 does retain a time limit, but it is somewhere beyond 10 minutes, which allows all reasonable matches to be saved without issue; it is known a limit exists because abnormally long matches and Multi-Man runs cannot be saved.
When saved, replays will be named
In Smash 4, players can save replays by pressing Y on the 3rd end-match-results page where it displays the detailed falls and KOs. Replays cannot be saved in Solo mode. Up to 64 replays can be saved in the 3DS version. The Wii U version allows around 230.
Prior to June 30, 2009, players could send their Brawl replays to be used for the Smash Service; after June 30, no more replays, custom stages, or screenshots would be accepted. One month later, on August 1, replay data was no longer being sent. Replays used for Smash Service were all from Stadium mode, especially Home-Run Contest and Target Smash!!, due to their typically shorter length and file size.
In both versions of Super Smash Bros. 4, Share mode allows players to upload replays to the official servers. Shared replays can be made visible to the public or only to users on the player's Friend List. Viewers can alse download shared replays to their own console. However, as with other shared data, replays will be deleted from the server after 30 days.
In Super Smash Bros. for Wii U from version 1.1.0 onward, players can choose to upload their replays to YouTube. This can only be done with replays of less than about 3 minutes and 14 seconds in length, however, and the upload process may take a relatively long time (around half an hour at max length). The replay must be played back before the upload can begin; if the player manipulates the camera while this is happening, the resulting YouTube video will be affected accordingly.
The player can enter a title for their YouTube video, while the description field on the site is automatically populated with the game mode, stage and characters used. The video can be viewed in resolutions ranging from 144p to 720p. As replays uploaded on YouTube will remain viewable after future gameplay updates, the current version number is displayed at the beginning of the video.
Beginning in version 1.1.1, players can upload an automatically edited "highlight" version of a replay instead of a full length version. This is analogous to the implementation of Mario Kart TV videos in Mario Kart 8. The highlight function reduces a replay to a series of short clips totaling between 30 and 60 seconds, regardless of the original length. It generally favors showing KOs from high-knockback moves, and will also tend to include Final Smashes even if they do not KO. The first and last few seconds of the match are always included, although the starting countdown is omitted. The behavior of the highlight function is not 100% consistent; if used on the same replay multiple times, it is sometimes possible for different clips to be selected.
Contrary to what may be expected, a replay is not saved as a video recording of the match. Instead, the input data from the match, the match's random number seed and the general rules are saved, so when a replay is watched, the game in fact re-generates the match from the data. This makes replays much smaller in file size than a video file, and it also allows pausing and camera movement during the replay.
Replays do not save the players' names, but this can be changed with a cheat code. For online battles, the game saves each player's server number and client number. When a player battles online, the player is seen as player 1 on his screen (client), but that may not be true for the server. In saved replays, each player's color and the numbers above the characters' heads indicate the client numbers (the ones that were seen on the screen of the one who saved the replay), whereas the order in which the character portraits appear on the bottom indicate the server numbers.
While playing with default settings or online in With Anyone mode, the characters' scores will not appear on the screen. However, when battles are saved as replays, the replays will show the score numbers above the characters' icons as if playing with the Score Display setting turned on.
In Brawl, replays do not save the input data from CPU players; instead, each CPU player simply re-plays the match from scratch. The discovery of this fact was the final nail in the coffin for the rumour that the AI was capable of learning, as if this were possible, any replay involving CPUs would desync without having stored each CPU's "learning state" (as the CPUs would otherwise use new tactics in old situations), which is disproven.
Because replays in Brawl and Smash 4 record inputs and the random number seed rather than the actual match, discrepancies are common compared to other games that are capable of saving entire matches to the system memory.
If a character or other element is loaded during a match faster than expected (such as because of pausing or online lag), then the replay of that match will "freeze" and finish loading the element before it can continue.
A common error noted in replays is that they may "desync" over time; the effects vary, though among the most common are actions occurring that did not previously occur, excessive lag followed by significantly increased playback speed, and the replay abruptly ending. With the Pokémon Trainer, particularly unusual effects can occur, such as him sending out a Pokémon which never loads or leaves the revival platform . Replays of Wi-Fi matches are more likely to desync than local matches due to the frequent lag experienced in games, but local replays can also be subject to the problem. The cause of "desyncs" is unknown, though it is speculated it has to do with save data of replays becoming corrupted by some outside factor. In addition, it is possible for a replay that plays fine to randomly desynchronize when played again, and after some tries, play correctly again. Some Special Brawl modifiers can especially be responsible for desyncs, as some modifiers like Curry and Speed directly affect the speeds of characters and other actions.
In Super Smash Bros. 4, players are warned after saving their first replay that certain updates to the game can potentially cause replays to not function; all updates that adjust game balance prevent the playing of older replays and provide an option to mass-delete them.
When uploading a replay to YouTube, there's a small chance that, at some point during the process of converting the replay into a video, the music will suddenly stop playing for a few seconds. There is also a bug where after uploading a video, the game will erroneously state that the post was cancelled. Additionally, posting a video disables the ability to post screenshots on Miiverse or take screenshots using the Wii U's Image Share feature. In order to post screenshots online again, players have to restart their game.