So What’s the Deal with Rollback Netcode, Anyway?

Critically acclaimed fighter King of Fighters XIII is being rereleased with the subtitle Global Match on the Nintendo Switch and PlayStation 4. Aside from the gorgeous rotoscoped sprite work and deep combo system, the main selling point of the new release is the implementation of rollback netcode to the great joy of fighting game fans across the world.

To non-fighters, it may seem odd that a change in a game’s netcode is met with so much excitement, but the shift towards rollback netcode helps address one of the biggest issues with online fighting games.

The ideal for all fighting games is for online play to get as close to offline play as possible. This is complicated by a myriad of factors, such as bandwidth, the use of a wired connection instead of wi-fi, and more. The old industry standard for this was delay-based netcode. Delay-based netcode works by delaying the frames of inputs by the same amount so that they can theoretically occur at the same time.

The word theoretically is doing some heavy lifting in the previous statement. It would be fine if everyone’s internet connection were the same all the time, but we all know that isn’t the case. The differences in ping can cause the frame delays to fluctuate rapidly, and that can lead to increased slowdown and freezing. It obliterates any semblance of consistency compared to offline play. Combo routes that are easily performed online are suddenly dropped all because an input came out later than it should have.

I played a couple of games of Ultimate Marvel vs Capcom 3 recently to test the difference from delay-based online to offline. The difference was immediate, and I applaud Capcom for giving me a very convenient excuse for when I lose against my friends. It was like playing a luck-based mission to see if I could follow up a launcher with an air combo.

Rollback takes a different approach to the online dilemma. It instead tries to guess every possible input either player makes to keep the game moving. If the predicted inputs differ from the actual ones, it “rolls back” to the correct input. In practice, this leads to a smoother, more consistent gameplay.

The advantages of rollback would be put on full display during the pandemic. With players unable to attend local scenes, good netcode became one of the make-or-break points for fighting games. Not having rollback in your game nowadays practically guarantees that it is dead on arrival without a large existing player base. I know more than a few people who decided to play Multiversus just because it had rollback. It’s both a selling point and a soft requirement for most fighters at this point.

Rollback’s strengths don’t just bolster new releases; they’ve revitalized old games as well. Arc System Works alone has updated Guilty Gear XX Accent Core Plus R, Blazblue Centralfiction and Persona 4 Arena Ultimax with the new netcode. Most recently, the team behind Dragon Ball FighterZ announced that rollback would be coming to the game soon.

There are a few games that frustratingly don’t seem to be getting rollback netcode anytime soon, such as Super Smash Bros Ultimate, which is a shame. But with high-profile releases like Street Fighter 6 and Tekken 8 confirmed to have rollback, it feels like fighting games have finally caught up with the rest of gaming in terms of emphasizing online play.

Desmond Leake is an intern for Paste‘s games section.