Have you ever built a massive 4-platform mob farm in survival, only to sit at the bottom and watch zero mobs fall down? Mob farm failures almost always come down to misunderstanding the game's spawning algorithm and mob caps.
The Global Hostile Mob Cap (70)
In singleplayer (or per player in 1.18+ multiplayer), the game caps hostile mobs at 70 per player. Once 70 hostile mobs exist in loaded chunks, no new mobs will spawn anywhere in your world!
The 128-Block Despawn Sphere
Mobs spawn between 24 and 128 blocks away from the player. Any mob that moves further than 128 blocks from the player instantly despawns!
If there are unlit dark caves below your mob farm within 128 blocks of your AFK spot, mobs will spawn in those caves, fill up the 70 mob cap, and completely shut down your farm.
How to Fix Low Farm Rates
- Build your AFK Platform high in the sky: Stand at Y=200 above an ocean so the 128-block sphere around you does not touch any underground caves.
- Ensure Light Level 0: Since version 1.18, hostile mobs only spawn in complete darkness (Block Light = 0).
- Use Tinted Glass or Slabs: Prevent accidental spawn blocks on roof surfaces.
Calculate farm XP and mob drops with our Mob XP Calculator!
Measure the farm instead of trusting a headline rate
- Empty the collection system and record the starting XP level.
- Run the farm for five minutes under normal server conditions.
- Count kills or collected drops and multiply the result by twelve for an hourly estimate.
- Repeat the test at a different AFK position and keep the better verified result.
Why two identical farms can perform differently
Spawn rates depend on edition, simulation distance, nearby players, eligible spawning spaces, mob caps and the time mobs remain alive. Caves or dark surfaces outside the farm can consume spawn attempts. On multiplayer servers, other players may load additional spawning areas or change how the cap is shared.
The fastest improvement is often not adding more platforms. First prevent spawns outside the farm, shorten transport and kill time, and confirm the collection system is not backed up. Use the Mob XP Calculator to translate a measured kill rate into expected XP, but treat ranged XP drops as estimates.
