Anti-Dupe Guard

# AntiDuplicationGuard
The most comprehensive item duplication prevention plugin for Paper 1.21.x servers.
Stop losing your economy and server integrity to item duplication exploits. AntiDuplicationGuard runs silently in the background, detecting and blocking over 20 known duplication methods in real-time — before your players can profit from them.
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What It Protects Against
AntiDuplicationGuard covers every major duplication vector known to Minecraft 1.21.x:
Inventory & Container Exploits

Bundle-in-bundle nesting & rapid bundle click duplication
Anvil close-with-full-inventory item duplication
Shulker box break-while-open duplication
Hopper overflow duplication via blacklisted items
Grindstone enchantment output duplication
Crafting table shift-click overflow duplication
Villager trade rapid-click duplication

World & Block Exploits

Piston-push duplication (configurable material list)
Nether & End portal item entity duplication
Gravity block (sand/gravel) torch & rail duplication
Dragon egg teleport duplication

Player Behavior Exploits

Death duplication (open container on death)
Disconnect duplication (logging out with container open)
Book & quill data exploit (rate-limited edits)
Fishing exploit (abnormal catch rate detection)
Vehicle (boat/minecart) rapid-spawn duplication
Creative mode item injection into survival inventories
Macro detection via rapid inventory click rate-limiting

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Features
Real-Time Admin Alerts
Get instant in-game notifications the moment a duplication attempt is caught. Toggle your personal alert stream on or off with a single command. Alerts show the player name, exploit type, item involved, and location.
Detailed File Logging
Every detection is asynchronously written to plugins/AntiDuplicationGuard/logs/antidupe.log with full timestamps, player UUIDs, world coordinates, and item data. Perfect for ban appeals and investigations.
In-Game Log Viewer GUI
Browse the full detection history without ever leaving the game. The paginated 54-slot GUI lets you scroll through all logged events or filter by a specific player name.
Fully Configurable
Every single detection module can be individually enabled or disabled. Adjust thresholds, blacklists, severity levels, alert formats, and more — all through a clean config.yml. Hot-reload in seconds with /adg reload.
Blacklist System
Define specific items that should never be duplicated. The blacklist is enforced across pickup, container transfers, hopper movement, and crafting outputs simultaneously.
Bypass Permission
Give trusted staff or plot admins a bypass permission so creative builders aren't flagged during legitimate work.
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Commands
| Command | Description |
|---|---|
| /adg reload | Hot-reload the configuration |
| /adg alerts | Toggle your personal alert notifications |
| /adg logs [player] | Open the in-game paginated log viewer |
| /adg check <player> | View a player's 5 most recent detections |
| /adg clearlogs | Clear all in-memory detection logs |
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Permissions
| Permission | Description |
|---|---|
| antiduplicationguard.admin | Access to all /adg commands |
| antiduplicationguard.alerts | Receive real-time detection broadcasts |
| antiduplicationguard.bypass | Bypass all dupe detection checks |
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Compatibility

Paper 1.21.x (Folia-friendly architecture)
Vault — Economy-aware alert formatting
PlaceholderAPI — Use player placeholders in alert messages
LuckPerms — Permission node compatible
Multiworld — Per-world detection works out of the box
No dependencies required — runs standalone

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Configuration Snapshot

YAML:

detection:
  bundle-dupe: true
  anvil-dupe: true
  shulker-break-dupe: true
  gravity-block-dupe: true
  dragon-egg-dupe: true
  death-dupe: true
  disconnect-dupe: true
  book-exploit: true
  fishing-exploit: true
  vehicle-dupe: true
  crafting-dupe: true
  villager-trade-dupe: true
  grindstone-dupe: true
  hopper-overflow: true
  rapid-click: true
  piston-dupe: true
  portal-item-dupe: true
  creative-injection: true
alerts:
  format: "&c[ADG] &7{player} &ctriggered &e{type} &7({item}) at &f{world} {x},{y},{z}"
  log-to-file: true
  broadcast-to-admins: true

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Notes

This plugin uses event cancellation as its primary prevention method — it does not delete items after-the-fact. This means zero rollback lag and no false economy corrections needed.
Detection thresholds (click rate, crafting speed, fishing rate, etc.) are all tunable to match your server's playstyle without generating false positives.

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Built for server owners who take economy integrity seriously.

Anti-Dupe Guard v1.0

Overview Updates (1) History