No Mob Farms

This is a Fabric server-side mod that detects when mobs originating from certain chunks or spawners die too frequently and reduces the spawn rates for those chunks/spawners.

Natural Spawner Nerf

This applies to "naturally spawned" mobs (that is, not through a mob spawner or structure generation), including the ones that continuously spawn in structures like Guardians.

The algorithm can be configured through the *nomobfarm.properties* file:

natural_slowdown_rate=1000   # Rate at which mob spawns are slowed down relative to the
                             # mob death frequency. Higher values lead to longer intervals in which
                             # mobs won't spawn.
natural_recovery_rate=3.0E-4 # Rate at which the spawn algorithm goes back to normal
                             # when mobs aren't dying.. It's essentially the rate at which the algorithm
                             # "forgets" how many mobs died.
natural_max_wait=100000      # Maximum interval (in ticks) in which mobs won't spawn.
natural_min_deaths=0         # Minimum number of mob deaths to trigger the slowdown

With these default values, the algorithm is moderately aggressive. It quickly curbs spawn rates when more than a few mobs from the same chunk die in a short time (because rapid, consecutive spawn batches in the same area are indicative of spawn mechanics abuse), but still allows mobs to spawn once in a while. Decrease the value of slowdown_rate to make it more conservative, increase max_wait and decrease recovery_rate to further reduce the rates for suspicious chunks

Mob Spawner Nerf

This applies to mob spawner blocks. The default values are:

spawner_slowdown_rate=30
spawner_recovery_rate=0.001
spawner_max_wait=10000
spawner_min_deaths=15

These values are rather conservative because, unlike for the other type of spawn mechanic, there's no obvious sign that the mobs are being spawned inside of a farm, at least based purely on the spawn/death rates, and also because spawners already have their own delay. This configuration will progressively slow down the spawner after at least 15 mobs die, though still allowing some mob spawns once in a while and allowing the spawner to go back to normal if its mobs aren't dying for a while (or aren't spawning at all), as long as the chunk remains loaded (and ticking).  The idea is that a player using the spawner legitimately would likely be discouraged by the slowdown and leave, allowing it to go back to normal after a while, while a farm would have to be used for a longer time to be actually worth building, which would cause the spawner to reach a high number of cumulated deaths and take a lot of time to go back to normal.