The online problem
Fighting games depend on precise timing, often measured in single frames of about 1/60 of a second. Over the internet, though, information takes time to travel. A button press on your console reaches the opponent’s after a delay that depends on distance, hardware and the quality of the connection. Even a modest delay of a few dozen milliseconds is several frames, which is enough to change the outcome of an exchange.
Netcode is the software that decides how the game deals with this delay. There are two broad approaches, and the difference is why online play has changed noticeably over the years.
Delay-based netcode
The older method is delay-based. The game waits until it has both players’ inputs for a given frame before it advances. To keep the two machines in step, it adds a fixed input delay: your button press is held back for a few frames so the opponent’s input has time to arrive.
This is simple and consistent, but the cost is felt directly. The higher the ping, the more delay is added, and every action feels sluggish. If the connection becomes unstable, the game may freeze while it waits. Timing-sensitive skills, such as reacting to a fast attack or punishing on a narrow window, become harder, because the delay is not what the player trained with.
How rollback works
Rollback netcode takes a different path. Instead of waiting, each game runs immediately using your own inputs and a guess about the opponent’s. The usual guess is that the opponent keeps doing whatever they were doing in the last frame they sent, for example continuing to hold a direction.
When the real input arrives, the game compares it with the guess.
- If the guess was right, nothing visible happens.
- If the guess was wrong, the game rewinds to the frame where the real input should have applied, replays the intervening frames with the correct input, and catches up to the present.
All of this occurs in a fraction of a moment, usually within a single displayed frame. Because the local controls always respond right away, the game feels much closer to offline play, with only a small fixed delay for stability. The trade-off is that the simulation must be able to save, load and rerun its state quickly and identically on both machines, which makes development more demanding.
What players notice
Rollback usually hides its work, but errors show up when predictions fail.
- Visual jumps. If the opponent’s character was guessed to be walking but actually jumped, it may seem to pop to a new position when the correction happens.
- Missing frames. When many frames need to be replayed, the game may skip some of the display to keep up.
- Changed outcomes. An attack that looked blocked on your screen can turn into a hit once the corrected sequence plays out. Such cases feel unfair in the moment, though they reflect the game fixing its earlier guess.
Because fighting games follow frame-exact rules, one corrected frame can change a combo’s result. The more frames that are rolled back, the more noticeable the effect.
Where rollback runs into limits
Rollback does not remove the underlying problem of distance and connection quality.
High ping. If the delay is large, the number of frames that must be guessed grows. Most implementations set a maximum rollback window. Beyond it, the game stalls or adds delay, since it cannot guess that far ahead and stay playable.
Unstable connections. Jitter, meaning delay that varies from moment to moment, and packet loss, meaning data that never arrives, cause irregular corrections. A connection with a steady high ping can sometimes feel better than one with a lower average that fluctuates.
Wireless networks. Wi-Fi often introduces jitter, which is why many players prefer a wired connection when they can use one.
Uneven experience. Each machine sees its own version of events, and differences between them can mean one player feels the matchup went differently than the other did. Which player benefits can vary from moment to moment, and rollback is not guaranteed to treat both players identically.
Hardware and performance. Rerunning several frames in a single frame period requires processing power. A weaker machine can struggle, and visible stutter or slowdown follows.
Fairness is about more than the code
The question of whether an online match is fair depends on several factors beyond the algorithm: the physical distance between players, the quality of each connection, the matchmaking rules, and whether the game gives both players similar information. Matchmakers that prioritise connection quality may give better matches but longer waits, a trade-off also found in discussions of queue time tradeoffs in other competitive games.
Because outcomes also depend on player skill, rating systems add their own complexity. Players of differing skill and connection quality can produce results that mix the effects of both, which is one reason a skill rating from online play should be read with some caution.
Practical advice for players
- Use a wired connection whenever possible.
- Prefer opponents with a lower ping, and treat a stable connection as more valuable than a very low one that varies.
- Learn how your game reports connection quality, and be willing to leave a match that is unplayable.
- Expect online play to differ from offline, and adjust by reacting less to quick visual cues and relying more on anticipation. Slow and obvious attacks remain easy to see, while fast ones are less dependable.
- Be cautious about drawing conclusions from a loss with a poor connection. A bad experience is not always a reflection of skill.
Rollback is a clear improvement for most players, and it has made online fighting games far more playable. It is still a way of coping with delay, not abolishing it.