Nintendo 64 emulator just implemented rollback netcode for the entire library: ‘It was honestly not that hard’

I’ve always loved the clean simplicity and disgusting combo game on offer in the original Super Smash Bros. but it’s hard to actually get a game with other humans together in 2026. The same goes for anything that’s most easily played on archaic hardware. While several emulators have netplay features, anything requiring twitch reactions tends to feel noticeably better in local multiplayer. But that might be changing—at least for the Nintendo 64.

RMG-K, a fork of the RMG Nintendo 64 emulator, received an update May 14 (via Kotaku) which implemented rollback netcode for the entire emulator, though developer CigNus has noted it’s currently limited to two-player sessions. Bluesky user Grasluu00 posted a video of GoldenEye multiplayer using the new feature, saying “Input delay is greatly reduced and desyncs are far more uncommon. This morning we managed to play from Spain to Australia with 4 frames of delay! Before this we had to do 9!!!”

If you’re not familiar with rollback netcode or why it causes crowds at fighting game tournaments to erupt into applause when its name is said, it’s a miracle of online multiplayer tech that makes fast-paced multiplayer games playable even with rough connections.

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While delay-based netcode requires both parties to catch up before button presses are honored on-screen, delay-based netcode makes predictions about what inputs will come next and quickly corrects itself when it’s wrong. The result is a degree of responsiveness you just can’t get with delay-based play.

Rollback’s implementation in RMG-K uses the GekkoNet framework, as creator Heat shared in a post on X. The same framework is being used in a fan project to port the PS2 version of Street Fighter 3: 3rd Strike natively to PC. Programmer NyxTheShield, who worked on rollback for RMG-K, said on X that GekkoNet “did most of the lifting” and adding rollback “was honestly not that hard.” I wonder if coders ever lose track of the fact that, from the sidelines, this all sounds like sorcerers discussing magic spells.

While it’s hard to say how it feels in any given game—the N64 has lots of multiplayer games—but NyxTheShield posted footage of Smash 64 in action on X and it seems to work well.

It’s worth noting that the RMG emulator’s original creator appears to have criticized the RMG-K fork for its use of AI in coding. “RMG-K is insulting, they took RMG’s code, vibe coded changes with Claude and then have a donation button in the ReadMe of the project,” developer Rosalie241 said yesterday on Reddit (while I can’t strictly verify that this is the same Rosalie who created the emulator, the account is five years old). “As someone who has spent years making RMG the way it is without any LLM assistance, seeing these vibe coded forks pop up is just depressing and just sad.”

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Coders involved with the project like NyxTheShield and CigNus have referenced their usage of AI in the past on social media, with Nyx stating on X that this rollback feature was implemented with using Codex as “an automation/helper … like in every workspace on the planet.”