WorldSlim

Reduce Minecraft world file size by automatically cleaning chunks that players barely visit. Three layers of defense catch what vanilla autosave would otherwise commit to disk.

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What it does

Modern Minecraft (1.18+) keeps chunks loaded much longer than a player's view distance, and autosave writes them all to disk regardless of activity. WorldSlim hooks every layer of that pipeline:

1. ChunkUnloadListener — when a chunk does unload, intercept the save if InhabitedTime is low.
2. AutosaveShield (new in 2.0) — every 2 seconds, pre-emptively clear the dirty flag on loaded low-InhabitedTime chunks so autosave skips them.
3. ChunkCleaner — periodically rewrite region files, removing chunks that slipped through the first two layers.

Player activity (placing blocks, attacking mobs, opening containers, picking up / dropping items) marks chunks as "force-save" so they survive cleanup.

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Highlights

• Three-layer architecture — unload + autosave + region rewrite. Aggressive without being unsafe.
• File-based ChunkRegistry — managed/force-save state stored in plugins/WorldSlim/data/, survives server restarts and Leaf/Moonrise's chunk-PDC strip. Crash-safe (lost marks degrade to "leave it alone").
• Aggressive mode (cleanup.aggressive: true) — restores the pre-1.0.6 cleanup logic, achieves 90%+ cleanup rate on fresh servers. Off by default to protect builds on established worlds.
• Diagnostics — /worldslim diagnose for runtime counters, /worldslim scan for raw-NBT inspection of any region file, /worldslim chunk for full decision-tree of the chunk you're standing in.
• Daily-rotating file logger at plugins/WorldSlim/logs/, configurable level.
• Config migration (new in 2.0.1) — new fields auto-injected on upgrade, preserving your edits and comments.
• Async + bounded — every disk operation runs off the main thread, with a 5-second timeout that safely skips when the server is busy.

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Compatibility

Server	PDC Persistence	Registry	AutosaveShield
Paper 1.21.x	Yes	Yes	Yes
Purpur 1.21.x	Yes	Yes	Yes
Folia 1.21.x	Yes	Yes	Partial
Leaves 1.21.x	Yes	Yes	Yes
Leaf 1.21.x	Stripped	Load-bearing	Limited

Requires Minecraft 1.21.x and Java 21.

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Commands

Command	Description
/worldslim status	Show plugin status and active configuration
/worldslim stats	Total chunks scanned/cleaned and space saved
/worldslim chunk	Full decision tree for the chunk you're standing in
/worldslim cleanup	Run a cleanup pass immediately
/worldslim diagnose [here]	Runtime diagnostic snapshot. Append here for current-chunk details
/worldslim scan	Parse the current region file's raw NBT and report what tags survived
/worldslim reload	Reload config.yml (also runs config migration)
/worldslim reset	Reset cleanup statistics

Aliased to /ws. Permission: worldslim.admin for mutating commands; worldslim.use for the read-only ones.

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Quick start

1. Drop the jar in plugins/, restart.
2. Default config is conservative (preserves any chunks that look pre-existing). Works without configuration on most servers.
3. On a fresh server — set cleanup.aggressive: true for the best cleanup rate.
4. On an established server with builds — leave aggressive: false (default) and let the registry track new chunks going forward.

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Configuration highlights

# Chunk lifetime threshold. Below this, chunks may be cleaned.
# Default 1200 ticks = 60 seconds.
min-inhabited-time: 1200

cleanup:
  interval-minutes: 30
  run-on-startup: false
  # Pre-1.0.6 cleanup behavior. Highly recommended for fresh servers.
  aggressive: false

autosave-shield:
  enabled: true
  interval-ticks: 40   # 2s

logging:
  file-enabled: true
  level: INFO          # DEBUG / INFO / WARN / ERROR

worlds:
  enabled: []          # if non-empty, ONLY these worlds are managed
  disabled: []         # always-skipped worlds

Full default config (with all comments) is generated on first run.

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Reporting issues

Please include:

• /worldslim diagnose screenshot
• Latest log from plugins/WorldSlim/logs/
• Server type and version