Entity Detective

Entity Detective

Entity Detective is a server-side Fabric mod built for one job: find entity-related lag fast. One command tells you which entity types are costing the most MSPT, where lazy mobs are silently accumulating, and where persistent creatures will never despawn — across every loaded dimension at once, no client mod needed. Works in singleplayer without enabling cheats.

What it does

• Hotspot scan — Run a 20-tick sample across all dimensions and get back the top-5 most expensive entity types ranked by MSPT, with no arguments needed — a fast first pass when you don't know where to look.
• Lazy mob detection — Pinpoint mobs stranded in chunks with no player within 128 blocks — the exact threshold Minecraft uses for despawn checks — where the server will never clean them up naturally
• Persistent mob detection — Find name-tagged mobs, item-holders, leashed animals, and vehicle riders that will never despawn even when they do tick.
• MSPT profiling — Measure how many milliseconds per tick any entity type is consuming, or profile every type at once sorted by cost, or just examine every entity inside a variable chunk range
• Chunk loader detection — Server load is often caused by chunk loaders. Find them fast. List all active portal chunk loaders (paired OW ↔ Nether) and ender pearl stasis chambers across every dimension.
• Block entity ticking audit — Use --ticking-only to find which block entities in a large farm actually ticked during an observation window, and --debug to see per-position tick counts instead of aggregate MSPT.
• Player profiling (nark) — Measure the MSPT cost of all entity types in the 21×21 chunk range surrounding any online player, to find what's expensive near their location.

Quality of life features

• Per-dimension summaries — See every entity type sorted by count, one block per dimension, across overworld, nether, and end simultaneously
• Clickable teleport links — Every chunk header and individual entity line is clickable in chat and pastes `/tp x y z` directly to the chunk centre or exact entity location
• Live mob cap — Check current vs. maximum entities per category with colour-coded saturation so you can spot mob cap pressure at a glance
• Command alias — Available as both /entitydetective and /ed

Command structure

/entitydetective
├── mob <category>
│   │   category: monster | creature | ambient | axolotls | water_creature | water_ambient
│   │   (bare)              — Type-count summary per dimension
│   │   --lazy-only         — Type-count table, non-persistent mobs in lazy chunks
│   │   --persistent [subtype]  — Type-count table, persistent mobs only
│   │       subtype: all | name-tagged | holding-item | structure-spawn | in-vehicle | leashed | custom
│   │   --world <dim>       — Scope to overworld | nether | end
│   │   --range <chunks>    — Scope to (2N+1)×(2N+1) chunk square (0 = single chunk)
│   │   --detail            — Expand to chunk-grouped entity list with clickable /tp links
│   └── cap                 — Live mob cap (current vs max, colour-coded)
│
├── entity
│   │   (bare)              — Summary of all entity types by count, per dimension
│   │   --lazy-only         — Type-count table, non-persistent entities in lazy chunks
│   │   --persistent        — Type-count table, persistent entities only
│   │   --world <dim>       — Scope to a specific dimension
│   │   --detail            — Expand to chunk-grouped entity list with clickable /tp links
│   ├── --range <chunks>    — Instant census of every entity type within range (0 = single chunk; no tick window)
│   ├── locate <type>       — Locate any entity type (tab-complete from live world, substring match)
│   │       --lazy-only, --world <dim>, --range <chunks>, --detail
│   │       --ticking-only  (block entities only) — filter to positions that actually ticked
│   ├── profile <type> [ticks]
│   │       Measure MSPT cost over a tick window (default 100 ticks / 5 s; max 6 000 ticks / 5 min)
│   │       --world <dim>, --range <chunks>
│   │       --debug         (block entities only) — per-position tick counts instead of aggregate MSPT
│   └── profile all [ticks]
│           Profile every entity type simultaneously, sorted by MSPT cost descending
│           (bare): all dimensions | --world <dim>: one dimension | --range <chunks>: local
│
└── item
    │   (bare)              — Dropped item summary per dimension, colour-coded by severity
    │   --lazy-only         — Type-count table, lazy chunks only
    │   --world <dim>       — Scope to a specific dimension
    │   --range <chunks>    — Scope to chunk square around your position
    │   --detail            — Expand to chunk-grouped item list with clickable /tp links
    └── locate <item_id>
            Find chunks with a specific item type (tab-complete, substring match)
            --lazy-only, --world <dim>, --range <chunks>, --detail

chunks                      — Detect active chunk loaders across all dimensions
    ├── loaders             — Portal loaders only (paired OW ↔ Nether lines)
    └── stasis              — Ender pearl stasis chambers only
        Coordinates are clickable /tp when you're in the matching dimension

hotspot                     — Top-5 entity hotspot scan (20-tick sample, all dimensions)

nark <player>               — Profile all entity types in the 21×21 chunk range around an online player

--detail must always be the last flag. --range and --world are mutually exclusive. Use /ed as a shorthand alias for /entitydetective.

Why lazy and persistent mobs matter

Lazy mobs are non-persistent mobs in chunks with no player within 128 blocks — the exact threshold Minecraft's despawn logic uses. Because those chunks never tick entities, the normal despawn check never runs. Mobs accumulate there indefinitely. Use --lazy-only to get a type-count table of what's building up, then add --detail for chunk-grouped clickable /tp links to teleport directly to the problem.

Persistent mobs are flagged by the game engine to never despawn, even in fully-ticking chunks. This includes name-tagged mobs, any mob that has picked up a dropped item off the ground, leashed animals, and mobs riding vehicles. Because they never despawn, they accumulate over time and increase the server's tick cost. Use --persistent to see where they are building up, and `--persistent ` to narrow to a specific cause.

Sample output

/entitydetective mob monster --lazy-only (type-count table)

-- lazy monster [overworld]: 45 entities --
  minecraft:zombie      28
  minecraft:skeleton    12
  minecraft:creeper      5
Total: 45 entities across 3 types

/entitydetective mob monster --lazy-only --detail (chunk-grouped, clickable)

-- monster [overworld] (lazy, --detail): 45 entities in 2 chunks --
  Chunk (12, -4)  ×  31  →  /tp @s 192 ~ -64
    [196, 63, -61]  —  minecraft:zombie
    [191, 64, -68]  —  minecraft:skeleton "Bob"  (name tagged)
    ...

/entitydetective entity profile all --range 10

-- Base Profile: 10-chunk range (100 ticks) --
    3.636mspt  TOTAL ×102
    1.779mspt  avg:  0.040ms  piglin ×44
    1.188mspt  avg:  0.043ms  hoglin ×28
    0.402mspt  avg:  0.040ms  strider ×10
    3.636mspt  TOTAL ×102

/entitydetective item (severity-coloured)

-- Item Types [overworld]: 2 847 items --
    2 130 items  (142 entities)  minecraft:cobblestone   ← red
      480 items  ( 48 entities)  minecraft:gravel        ← yellow
       12 items  (  4 entities)  minecraft:diamond       ← green

No client mod required · Works cross-dimension · Singleplayer compatible · Respects LuckPerms

Singleplayer world owner has full access without enabling cheats. On servers, requires op level 2 or the entitydetective.command LuckPerms node.
Releases · Source · License: MIT