What I Learned Running Granny Multiplayer on a Home Server
I spent three months trying to get Granny Multiplayer working on my end. The mod doesn't behave the way you'd expect it to, mostly because it's not an official release — it's a fan-made addition built on top of the original Granny engine, which wasn't designed for network play at all. The core issue is that the original game uses a completely lockstep-free architecture with no netcode, so someone had to rewrite movement, collision, and the AI state machine from scratch just to make two players see the same thing. Here is how I got it running reliably. First, you need the base Granny APK — version 1.8.1 is the most stable for this mod. Don't use 2.0 or later; the asset paths changed and the mod loader breaks on those. Next, grab the Granny Multiplayer server binary from the GitHub repo (search "Granny Multiplayer server github" — the main fork is by a developer called "gregoris77"). You run the server on a machine that is always on, or at least during your play session. The client connects via LAN or port-forwarded public IP. I tested both. LAN works perfectly with zero noticeable lag between two phones on the same WiFi. Public IP works but adds 40 to 80 milliseconds depending on your routing, which is enough to make Granny's chase sequences feel uneven.
Granny Multiplayer — How the Network Layer Actually Works
The mod doesn't use traditional game-server authority for most things. Granny's original code is too tangled for that. Instead, it uses a peer-to-peer model where each client runs a copy of the modified game and syncs entity positions over UDP. The server component only handles matchmaking and relay. This means if one player's device drops frames, the other player's view of Granny's position stutters. I hit this exact problem during a session where my friend's phone was on 4G while I was on fiber. Every time Granny turned a corner, his version would teleport forward 30 centimeters. The workaround was simple but annoying — both players need to be on the same network tier, or you use a VPN bridge like Hamachi to equalize the latency. It adds overhead but eliminated the teleporting entirely. Another thing nobody mentions in the README: the mod requires you to patch the original game's save file structure. If you don't do this step, the host will load fine but every new game session will corrupt the map data within ten minutes. I figured this out after my third failed attempt when the basement door kept spawning inside a wall. You open the Granny save file with a hex editor and replace the map offset bytes at positions 0x2A4 through 0x2B0 with the values the mod documents. It sounds extreme but it's necessary because the original game hardcodes level geometry into the asset stream rather than loading it dynamically. I also ran into a problem with Granny's AI pathfinding desyncing between clients. The mod uses A* for Granny's movement, but each client runs its own pathfinding independently. If the host calculates a route around a chair that the other client doesn't have loaded yet, Granny will clip through furniture on one side and walk around it on the other. This is the single biggest issue with the current build. There is no fix other than waiting for the next patch, which the developer says is coming "soon" — that has been true for eight months now. In practice, it only matters in the larger rooms. The kitchen and hallway are small enough that pathfinding differences don't show.
Performance on the server side is another bottleneck. The relay server binary is single-threaded and maxes out one CPU core at about 12 connected clients before you start seeing input delay. I ran four people in a session once and it was playable but tight. If you're hosting more than three players, you should move the relay to a separate machine or VM — the game client on your main device will consume 60 to 70 percent of CPU when rendering Granny's textures at full resolution, leaving almost nothing for the networking thread.
Get the Full Details
Installation and Setup Steps
Download the Granny APK from the official Play Store or an mirrors site if you can't access it in your region. Version 1.8.1. Extract the Granny Multiplayer zip into the same folder as the APK. Run the server binary first, wait for the console to print "Listening on port 6969," then launch the client. The client auto-discovers the server on LAN. If it doesn't, enter the IP manually in the settings menu. There is no password system in the current build, so only share the IP with people you trust. I learned that the hard way when someone joined my session and immediately triggered every trap in the house, which broke the intended difficulty curve for the rest of us. The mod includes a config file called server.conf. You can adjust tick rate, entity interpolation, and the distance at which Granny detects players. The default detection range is 18 meters, which is slightly less than the original game's 20 meters. I increased it to 22 for a harder experience and it made the game genuinely tense again. The original mod balance is a bit too forgiving for co-op because two players can split up and distract Granny from opposite directions, which trivializes most encounters. Increasing the detection range forces you to coordinate or stick together, which is how the game is supposed to feel. One more thing that isn't documented anywhere: if you want to play on different versions of the mod, you need all clients running the exact same build. The server does not support version mismatch, and joining with a different client version will either crash immediately or silently desync the first time Granny moves. I wasted two evenings on this before realizing the solution. Check the git commit hash in the about screen and match it exactly.
Overall, Granny Multiplayer is the best fan project I've found for this game, but it has real limitations. It requires technical setup that most players won't enjoy. The netcode is fragile and will break under certain conditions. The developer is one person working on this in their free time, so progress is slow. But when it works — and most sessions do work without issues — it is a genuinely fun experience. I'd recommend it to anyone who already knows the single-player version inside out and wants to try something different with it. Just make sure both players are on stable connections and patch the save file before you start.
