Rollback Netcode

A network synchronisation architecture used in fighting games, and increasingly other competitive genres, in which each player's game client locally predicts (simulates) the opponent's current inputs rather than waiting for those inputs to be confirmed over the network, then immediately 'rolls back' and recomputes game state if the prediction proves incorrect when the actual input arrives. The alternative, delay-based netcode, inserts an artificial input buffer of several frames on both players to allow network packets to arrive before processing, creating a lag-like sluggishness even on fast connections. Rollback produces online play that feels nearly identical to offline play even at 80-120ms latency, because the client never 'waits', incorrect predictions correct silently, and at typical prediction error rates the corrections are nearly invisible. The GGPO library (created by Tony Cannon in 2007) provided the first accessible rollback implementation for fighting games, and games using it, Street Fighter III: 3rd Strike Online, UMvC3, Skullgirls, demonstrated the quality gap versus delay-based alternatives. The modern rollback expectation for new fighting games was set by Guilty Gear Strive (2021), Street Fighter 6 (2023), and Tekken 8 (2024). Rollback adoption is not universal: some older fighting games still run on delay-based netcode because rollback implementation requires significant engine access, and retrofitting it to legacy titles is costly. Dead or Alive 6, while technically advanced in gameplay, still uses delay-based netcode, a commonly cited reason competitive players avoid it online.