Viper Anti-Dupe

Viper Anti-Dupe is a high-performance, Server-Side ONLY configurable anti-duplication mod for Minecraft 1.21-1.21.11, 26.1-26.1.2, and 26.2. Blocks 25+ known dupe methods with zero client mods required. Fully configurable per-method choose what to block and what to allow.

Supported Versions

Version	Java	Status
1.21 1.21.11	21	Full support
26.1 26.1.2	25	Full support
26.2	25	Full support

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Purpose & Function

The core mission of this project is to give server administrators total control over duplication prevention on their server.

• Block Every Known Method: Covers book dupe, shulker box nesting, rail/piston/carpet dupes, entity cloning, trident dupes, TNT dupes, beehive dupes, tripwire dupes, string dupes, lectern dupes, gravity block dupes, NBT list dupes, item frame dupes, container desync, death dupes, chunk rollback, portal dupes, bundle dupes, crafter dupes, and more.
• Per-Method Config: Each dupe method is individually togglable no more all-or-nothing protection.
• Audit Logging: Built-in audit log tracks every blocked attempt with timestamps, player names, and dupe type.
• Known Dupable Items: Configurable list of known-dupable items with command management.
• Hot Reload: Change config on the fly no server restart needed.

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Dupe Methods Blocked

Method	Config Key	Default
Book Dupe	bookDupe	BLOCKED
Shulker Box Nesting	shulkerBoxDupe	BLOCKED
Rail Dupe	railDupe	BLOCKED
Carpet Dupe	carpetDupe	BLOCKED
Horse Quick-Move	horseQuickMoveDupe	BLOCKED
Stack Split	stackSplitDupe	BLOCKED
Hopper Dupe	hopperDupe	BLOCKED
Piston Dupe	pistonDupe	BLOCKED
Entity Dimension Dupe	entityDimensionDupe	BLOCKED
Trident Dupe	tridentDupe	BLOCKED
Bee Dupe	beeDupe	BLOCKED
Tripwire Dupe	tripwireDupe	BLOCKED
String Dupe	stringDupe	BLOCKED
Lectern Dupe	lecternDupe	BLOCKED
Tripwire Hook Dupe	tripwireHookDupe	BLOCKED
Gravity Block Dupe	gravityBlockDupe	BLOCKED
NBT List Dupe	nbtListDupe	BLOCKED
Item Frame Dupe	itemFrameDupe	BLOCKED
Update Suppression	updateSuppressionDupe	BLOCKED
Container Desync	containerDesyncDupe	BLOCKED
Death Dupe	deathDupe	BLOCKED
Chunk Rollback	chunkRollbackDupe	BLOCKED
Portal Dupe	portalDupe	BLOCKED
Bundle Dupe	bundleDupe	BLOCKED
Crafter Dupe	crafterDupe	BLOCKED

Enhance your server setup! Check out my other server-side mods over at : Fabric Server Essentials

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In-Game Commands

All commands use the /viperantidupe command tree. Requires operator level 2+.

Command	Description
/viperantidupe reload	Hot-reload config from file
/viperantidupe status	Show mod version, enabled state, blocked/allowed counts
/viperantidupe methods	List all dupe methods with current status
/viperantidupe get <method>	Check if a specific method is ALLOWED or BLOCKED
/viperantidupe set <method> <true/false>	Toggle a dupe method (true=allow, false=block)
/viperantidupe item get <id>	Check if an item is known-dupable
/viperantidupe item set <id> <true/false>	Set an item as known-dupable
/viperantidupe dumpitems	Dump all registered item IDs to a JSON file
/viperantidupe dumpknown	Dump known-dupable items list to a JSON file
/viperantidupe audit	Show the 50 most recent audit log entries

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Configuration

Edit config/viper-anti-dupe.json after first launch:

{
  "modEnabled": true,
  "loggingEnabled": true,
  "logFilePath": "logs/viper-anti-dupe-audit.log",
  "maximumItemNbtBytes": 32768,
  "maximumContainerNestingDepth": 3,
  "cancelSuspiciousTransactions": true,
  "knownDupableItems": {
    "minecraft:barrier": true,
    "minecraft:structure_void": true
  },
  "bookDupe": false,
  "shulkerBoxDupe": false,
  "railDupe": false,
  "carpetDupe": false,
  "horseQuickMoveDupe": false,
  "stackSplitDupe": false,
  "hopperDupe": false,
  "pistonDupe": false,
  "entityDimensionDupe": false,
  "tridentDupe": false,
  "beeDupe": false,
  "tripwireDupe": false,
  "stringDupe": false,
  "lecternDupe": false,
  "tripwireHookDupe": false,
  "gravityBlockDupe": false,
  "nbtListDupe": false,
  "itemFrameDupe": false,
  "updateSuppressionDupe": false,
  "containerDesyncDupe": false,
  "deathDupe": false,
  "chunkRollbackDupe": false,
  "portalDupe": false,
  "bundleDupe": false,
  "crafterDupe": false
}

Config semantics: false = BLOCKED (the dupe method is prevented), true = ALLOWED (the dupe method is permitted). This is by design a false-positive safe default blocks everything until you explicitly allow methods you trust. Setting a method to true does not enable any exploit it simply removes the mod's protection against it.

Hot-reload config in-game: /viperantidupe reload

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Installation

1. Drop the JAR for your Minecraft version into your server's mods/ folder
2. Install Fabric Loader 0.19.3+ (all versions)
3. Install Fabric API (required for all versions)
4. Start the server config auto-creates at config/viper-anti-dupe.json
5. Review and customize the config to your needs
6. Run /viperantidupe reload or restart the server

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Built for administrators who demand robust duplication protection with zero client overhead. Every dupe method is individually configurable block what matters, allow what doesn't.