How to undo an in-game save

Since 1.2.0, an in-game save is written after a second without changes. A mistaken save also replaces the previous one. In 1.3.0 earlier saves are kept on the device, and an automatic save state is made every five minutes.

In 1.2.0, in-game saves started being written to their file during play. Save data is written once it has stayed the same for a second, so a sudden shutdown loses recent saves less often.

But a save overwritten by mistake or damaged by a cheat is written in the same way. Earlier saves were not kept separately, so a mistaken save could not be undone.

The existing in-game save is now kept separately on this device when a game starts, before the core opens its save file. A copy is also kept before replacing it with a save from a file, another emulator, Drive or an offline backup. A save identical to the most recent copy is not kept again.

Up to the five most recent are kept per game, at most 32 MiB each and 64 MiB per game in all; beyond that the oldest go first. Rolling back from In-game save history on the game information screen first adds the current save to the history and then replaces the files in one step, so a rollback can itself be rolled back. A game that is running is not rolled back.

This history is not included in Drive or offline backups. It is not a save to move to another device; it is a record for undoing a mistake on this one.

Games without in-game saves had a different problem. The automatic save was taken only when the app went to the background or the game ended, so progress in between was lost if the app closed. Now, every time five minutes of actual play add up, the in-game save and the automatic save are written together without stopping the game. Time spent paused, in menus or in the background is not counted.

Nintendo DS and PSP are left out of the five-minute save. A save state for them runs from several to tens of MiB, too much to write during play, so both still save only when the app goes to the background. Whether play can continue after the app is force-quit on a real device has not been checked yet.