Mob Stacking

Mob stacking merges nearby mobs of the same kind into a single entity that stands in for all of them. Two hundred zombies in a grinder become a handful of entities carrying a count, so the server ticks a fraction of the mobs it used to.

It works on EcoMobs and vanilla mobs alike, and needs nothing per mob — turn it on and it applies everywhere.

Config

Everything lives under stacking in config.yml.

stacking:
  enabled: true

  radius: 8 # How far to look for a stack to merge into
  max-size: 64 # The most mobs one stack can hold
  sweep-rate: 100 # How often (in ticks) to sweep for mobs that drifted together
  max-merges-per-tick: 20 # The most merges done in one tick; 0 is no limit

  # Whether killing a stacked mob kills the whole stack, dropping loot and XP for every
  # mob in it. When false, each kill takes a single mob off the stack.
  kill-whole-stack: false

  # Whether the death animation is hidden when a stacked mob is killed.
  hide-death-animation: false

  # Whether babies and adults are kept in separate stacks.
  match-age: true

  # The nameplate shown above a stack. %size% and %name% are replaced.
  nameplate: "&f%name% &7x%size%"

  # What never stacks. EcoMob IDs and vanilla entity types are both valid.
  blacklist:
    - villager
    - wandering_trader
    - ender_dragon
    - wither

  exclude:
    tamed: true # Pets and other tamed mobs
    leashed: true # Mobs on a lead
    mounted: true # Mobs riding something else
    ridden: true # Mobs carrying passengers
    named: true # Mobs already named, by a name tag or another plugin

Run /ecomobs reload to apply changes.

How mobs merge

A mob looks for a stack twice:

  • When it spawns. Every spawn method ends up here — natural spawning, spawners, breeding, spawn eggs, commands, other plugins — so nothing needs wiring up per source.

  • On the sweep. Every sweep-rate ticks, mobs within 48 blocks of a player try again. This catches mobs that wandered together long after they spawned.

Two mobs merge when all of this holds:

  1. They are the same kind — the same EcoMob ID, or the same vanilla entity type for plain mobs.

  2. They are both adults or both babies, unless match-age: false.

  3. Neither is excluded or blacklisted.

  4. The combined size fits inside max-size.

  5. They are within radius blocks of each other.

The mob joins the nearest stack that fits. The absorbed entity is removed and the one it joined grows by its size, so two stacks meeting merge into one rather than resetting to a pair.

Stack size is stored on the entity, so a stack survives chunk unloads, restarts, and anything else that takes it out of memory. A stack of one carries no data at all — it is simply a mob again.

Spawners

With stacking on, spawners don't spawn a mob per mob. A cycle is added to the nearest stack within radius, or spawned as a single mob already standing for the whole cycle, capped at max-size. See Custom Spawners.

max-nearby on a spawner counts a stack as every mob it holds, so the vanilla default of 6 stops a stacking spawner almost at once. Raise it on any spawner meant to feed a farm.

Merge cost

Merging a mob means looking around it for a stack to join, so the work grows with how many mobs are standing there. max-merges-per-tick (default 20) is the ceiling on that per tick — anything left over is merged on later ticks instead of holding the server up, and the stacks end up identical, just a moment later.

Raise it if mobs visibly take too long to stack on a busy server; 0 removes the limit and restores the old behaviour, which on a large farm could stall the server thread badly enough to be killed by the watchdog.

Nameplates

Stacks are labelled with nameplate, drawn above the mob:

A stack of 32 zombies labelled "Zombie x32" beside a spawner with its hologram
nameplate: "&f%name% &7x%size%"

%size% is the stack size and %name% is the mob's name — an EcoMob's display-name with its own placeholders already filled in, or the vanilla name otherwise. PlaceholderAPI placeholders work here, and are filled per viewer.

Nameplates are drawn clientside, so they do not touch the mob's real name and nothing else on the server sees them. An unstacked mob shows nothing.

A nameplate is only shown to a player who can see the mob. Behind a wall or underground it is hidden, and it comes back once the mob is in view again, updated every quarter of a second.

What happens on death

This is the setting worth thinking about.

kill-whole-stack: false (default)

One mob comes off the stack. The dead mob drops its own loot and XP as normal, and the remainder comes back immediately as a fresh mob at full health, carrying the new size.

The replacement is spawned, not healed, so what the stack was is carried onto it: whether its AI was taken away, whether it was a baby, and whether it came from a spawner. A no-ai stack stays a no-ai stack all the way down.

Every mob has to be killed one at a time. Best for survival servers, where a stack should be no more rewarding than the mobs in it.

kill-whole-stack: true

The whole stack dies at once, and pays out for every mob in it. A stack of 32 killed with one hit drops 32 mobs' worth.

Drops are rolled per mob rather than copied, for EcoMobs and vanilla mobs alike, so chance-based drops stay chance-based — a stack of 32 does not guarantee a 10% drop, it gets 32 rolls at it.

XP is the exception: vanilla hands out a fixed amount per mob, so the stack pays that amount per mob in it. Equipment the dead mob was wearing isn't handed out again either — armour and weapons aren't part of a loot table, and there is no knowing what the rest of the stack had on.

Best for grinders and arenas, where clearing a stack in one hit is the point.

hide-death-animation: false (default)

Whether the dead mob's body plays out its death animation. This applies to both settings above — the whole stack dying at once, and a single mob coming off the stack.

Left at false, the corpse tips over and fades out the way any mob does, taking about a second. On a stack killed one mob at a time that second is spent lying next to the replacement mob, so a fast grinder ends up with a pile of bodies on top of the live stack.

Set it to true and the corpse is taken away right after the kill, so the mob simply vanishes. Drops, XP, death messages, and everything else that hangs off the kill are unaffected — only the body goes early.

What never stacks

Only mobs stack in the first place. Players, armour stands, items, projectiles, and every other non-mob entity are ruled out by type.

On top of that:

  • blacklist — EcoMob IDs and vanilla entity types both work, so hollow_king and zombie are equally valid entries. The default list keeps villagers, wandering traders, and the two vanilla bosses out.

  • exclude.tamed — pets and other tamed mobs, so a player's wolves stay separate animals.

  • exclude.leashed — anything on a lead.

  • exclude.mounted — mobs riding something else, so a skeleton on a horse stays whole.

  • exclude.ridden — mobs carrying a passenger.

  • exclude.named — mobs given a name by a name tag or another plugin. EcoMobs' own names are drawn clientside and do not count, so a named EcoMob still stacks.

Set any of the exclude entries to false to let that group stack anyway.

Where to go next

  • Stack the spawners too: Spawner Stacking.

  • Spawner settings: Custom Spawners.

  • Make a mob: How to Make a Custom Mob.