Rollback
Also said as Rollback netcode, GGPO, Rollback networking
Your own inputs happen at once, and the game guesses that the other player is still doing what they were doing. When their real input arrives and differs, it reloads a saved state and quickly replays every frame since.
Your controls feel the same at 100 ms as they do offline, which is everything in a fighting game. In exchange, the other player sometimes jumps a few frames, and the game has to save and replay its entire state within one frame.
Say it
“Use rollback with up to 8 frames of prediction and 2 frames of input delay. Game state must save and restore in under 1 ms, and everything in the simulation must be deterministic.”
Where you’ve seen it
Tony Cannon released GGPO in 2006, and Street Fighter III: 3rd Strike Online Edition used it in 2011. Guilty Gear Strive built its own rollback in 2021, and GGPO went open source under the MIT licence in 2019.
Not to be confused with client-side prediction
Prediction replays only your own character against a server's word. Rollback restores the entire game state on each machine, and normally has no server at all.