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8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2

8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2 on HackerTube: recommended by 4 Hacker News commenters across 5 separate months, 2020–2025.

GDC Festival of Gaming

talk · advanced · evergreen

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A 2018 GDC talk by NetherRealm's Michael Stallone on the engine changes, optimizations and tooling needed to roll back and re-simulate up to 8 frames in 16 ms in Mortal Kombat and Injustice 2. It is a deep dive into deterministic rollback netcode.

Why Hacker News recommends it

HN treats it as the definitive practical talk on rollback networking in a shipped AAA fighting game.

people recommended it
4
separate months
5
strong recommendations
0
discussed on HN
2020–2025
“For an in-depth explanation, see this excellent GDC talk on its implementation in Mortal Kombat and Injustice 2”
— Oberdiah, Oct 2023, in “Ready Player Two – What the Multiplayer Web Can Learn from Video Games”

What HN commenters said

6 Hacker News comments link this video. Each one links back to its thread.

c4wrdMar 2025Recommends

For those who aren't in the video game development field and like technical content, I cannot recommend watching GDC's content enough (even better, attending!). Although this blog post isn't as detailed as I've seen them do in the past, I appreciate that game developers have the opportunity to share their wins like this externally. If you enjoy watching technical content and video games, the following videos are greatly entertaining deep dives into ludicrously technically complicated bugs or performance optimizations done to deliver the gaming experience that I myself take for granted. - I Shot You First: Networking the Gameplay of Halo: Reach: [link] - 8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2: ▶ this video - It IS Rocket Science! The Physics of Rocket League Detailed: [link] - [link]

in “Activision Cut Call of Duty's Build Time by 50%” · View on HN

OberdiahOct 2023Recommends

Specifically "Deterministic Rollback", as the clients don't wait for the server's response before displaying the change locally. For an in-depth explanation, see this excellent GDC talk on its implementation in Mortal Kombat and Injustice 2: ▶ this video

in “Ready Player Two – What the Multiplayer Web Can Learn from Video Games” · View on HN

dilapOct 2021Recommends

I guess it depends on how high a level you're looking at it from. Both lockstep and rollback are variants of the general approach of "shared deterministic simulation" where you're mostly just sending inputs. ("Mostly" 'cuz on reconnect or desync or whatever you'll probably want to send full state.) I really enjoyed this GDC talk on rollback networking: ▶ this video (From 2019.)

in “1500 Archers on a 28.8: Network Programming in Age of Empires and Beyond (2001)” · View on HN

syspecFeb 2021Recommends

Here's another great video on the subject: 8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2 ▶ this video One of my favorite topics, partially because there's not that much literature on the subject but it's so important

in “How fighting games use delay-based and rollback netcode (2019)” · View on HN

syspecJul 2020Recommends

Do you have a link to any blog posts, i would love to read about it. I tried to look on [link] , but development appears to be closed source? I'm just an outside observer, but i love the topic. For others like myself, this is a great GDC video to watch on the topic > 8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2 ▶ this video

in “Dolphin Progress May and June 2020” · View on HN

honkycatApr 2021Cites it

I do indie game dev as a hobby, and I have taken multiple classes on networked multiplayer, and I've also implemented VERY SIMPLE proof of concepts for multiplayer fighting games in Unreal Engine. I think what a lot of people are missing here is the context that there is STILL not a "make it multiplayer" button in game engines. They do NOT do most of the work for you for any facet of game development. Making games is still a ton of work. To name a few things that Unreal Engine does not do for you: networked movement prediction, acceptable LERPing to positions when client/host disagree, anticheat... basically it has a nice client/server model API you can use. You can annotate structs to efficiently be transmitted over the internet, and query the API to see if you are "host" or "client". There is an amazing talk on this from the Mortal Kombat creators about how long it took them to get their netcode right[0]. Now make that much harder when dealing with millions of players in one world, with mold-able terrain and an exotic networking stack. 0: ▶ this video

in “DreamWorld (YC W21) MMO raises all red flags” · View on HN

Topics & tags

Game programming & enginesNetworking & internet infrastructurenetcodefighting gamesgame enginesdeterminismgdc