MapSyncer for Xaero's World Map

A multi-platform Minecraft mod that syncs server-side explored areas to clients' Xaero's World Map. BiliBili GitHub

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Platform Support

Prioritizing modern versions. NeoForge didn't exist as an independent loader before 1.20.4. Forge provides no developer documentation after 26.1.

MC Version	Forge	NeoForge	Fabric
1.20.1	✅	—	✅
1.21.1	✅	✅	✅
1.21.11	✅	✅	✅
26.1	—	✅	✅

Client Dependencies

Supports both dedicated servers and integrated servers (single-player LAN sharing). On integrated servers, the host's Xaero's World Map save directory is reused as the map cache, eliminating redundant conversion.

Dependency	Requirement
Xaero's World Map	1.40.11+

Server Requirements

• Xaero's World Map is NOT required on the server
• Chunky or similar pre-generation tools are recommended

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Features

Feature	Description
Incremental Sync	CRC32 hash + timestamp comparison — only transfers changed regions
Streaming Load	Writes to Xaero directory as data arrives, triggers immediate reload per region
Bandwidth-Aware	Dynamic send rate adjustment to avoid blocking game network
Resumable Sync	Auto-resumes from interruption after reconnect (hash-based)
View-Distance Priority	Regions within player's view distance are prioritized
Dimension Support	Overworld, Nether, End, and mod dimensions (e.g. Twilight Forest)
Incremental Update	Server-side periodic/scheduled map cache regeneration
Cave Mode	Scans downward from a configurable height, outputs to caves subdirectory
Multi-Threaded Hash	Configurable parallel CRC32 computation on the client
Auto Sync	Automatically checks for newer server maps on join, no manual command needed

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Commands

Client Commands

Command	Description
/mapsyncer	Show help
/mapsyncer sync	Sync current dimension
/mapsyncer sync <dim>	Sync a specific dimension
/mapsyncer sync all	Sync all dimensions

Dimension arguments: overworld, the_nether, the_end, or mod dimension IDs like twilightforest:twilight_forest

Server Commands (OP required)

Forge/NeoForge uses /mapsyncer; Fabric uses /mapsyncerserver to avoid conflicts with the client-side /mapsyncer.

Command	Description
/mapsyncer generate	Generate cache for all dimensions
/mapsyncer generate <dim>	Generate cache for a specific dimension
/mapsyncer generate <dim> <x> <z>	Generate a single region
/mapsyncer generate <dim> --force	Force rebuild (clears existing cache)
/mapsyncer status	View generation progress and cache statistics
/mapsyncer incremental off	Disable incremental updates
/mapsyncer incremental tick [interval]	Enable periodic updates (20–72000 ticks)
/mapsyncer incremental scheduled [hour] [min]	Enable scheduled updates (default 04:00)

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Configuration

Client Config

Option	Default	Range	Description
hashThreads	CPU cores/2	1–cores	Number of threads for CRC32 computation

Server Config

Forge config: world/serverconfig/mapsyncer-server.toml (per-world) NeoForge / Fabric config: config/ directory (.toml for NeoForge, .properties for Fabric)

General [general]

Option	Default	Range	Description
enableDebugLogging	false	—	Enable debug logging
maxConcurrentRegions	4	1–16	Concurrent region conversion threads
maxSyncPacketSize	262144 (256KB)	64KB–1MB	Max packet size in bytes
syncSpeedLimitKBps	1024 (1MiB/s)	0–10240	Sync rate limit (0 = unlimited)

Incremental Update [incremental_update]

Option	Default	Description
incrementalUpdateMode	DISABLED	DISABLED / TICK / SCHEDULED
incrementalUpdateIntervalTicks	200	TICK mode interval (20 ticks = 1 second)
scheduledUpdateHour	4	Scheduled update hour (0–23)
scheduledUpdateMinute	0	Scheduled update minute (0–59)

Dimension Scan [dimension_scan]

Option	Default	Description
default_scan_mode	SURFACE	Default scan mode for unconfigured dimensions
default_cave_start	63	Starting height for CAVE mode

Dimension config format:

dimension_configs = [
    "minecraft:overworld|SURFACE|63|true|false|-64|384|384",
    "minecraft:the_nether|CAVE|63|false|true|0|256|256",
    "minecraft:the_end|SURFACE|63|false|false|0|256|256"
]

Format: dimensionID|scanMode|caveStart|hasSkylight|hasCeiling|minY|height|logicalHeight

• SURFACE: Scans downward from heightmap. For Overworld and End.
• CAVE: Scans downward from a fixed height. For Nether.

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Project Structure

libs/                   Abstract library layer (platform-agnostic, compiled as independent JARs)
├── core/               Pure Java core: MCA/NBT parsing, utilities
└── platform-api/       Platform abstraction interfaces, network payload definitions

mc-1.20.1/              1.20.1 version
├── shared/             Shared source (referenced by platform modules via sourceSet)
├── fabric/             Platform implementation (produces final mod JAR)
└── forge/

mc-1.21.1/              1.21.1 version
├── shared/
├── fabric/
├── forge/
└── neoforge/

mc-26.1/                26.1 version
├── shared/
├── fabric/
└── neoforge/

Pipeline

Server MCA files (region/*.mca)
        │
        ▼
    MCA Parser (pure Java, no Xaero dependency)
   Decompress → NBT parse → Extract chunk data
        │
        ▼
   Region Conversion (RegionConverter)
        │
        ▼
Encode to Xaero format (region.zip)
        │
        ▼
  Timestamp + Hash Cache (GenerationCache)
        │
        ▼
  Incremental Update Processor (optional)
  TICK mode / SCHEDULED mode
        │
        ▼
    Network Sync Protocol
  Hash comparison → View-distance priority sort
  Batched transfer + rate limiting
        │
        ▼
    Streaming Receive
  Write to Xaero directory as data arrives
        │
        ▼
   Xaero Reload Trigger (reflection)
  requestLoad → Map re-renders

File Storage

Server:
  <server>/server_map_cache/
  ├── null/              # Overworld
  ├── DIM-1/             # Nether
  ├── DIM1/              # End
  ├── caves/<layer>/     # Cave mode output
  └── generation_cache.properties  # Timestamp + hash cache

Client:
  <client>/xaero/world-map/Multiplayer_<IP>/     # Modern Xaero unified path (preferred)
  <client>/XaeroWorldMap/Multiplayer_<IP>/       # Legacy Xaero path (compatibility fallback)
  ├── null/mw$<worldId>/   # Overworld
  ├── DIM-1/mw$<worldId>/  # Nether
  └── DIM1/mw$<worldId>/   # End

Dimension Mapping

Dimension	Minecraft ID	Xaero Directory
Overworld	minecraft:overworld	null
Nether	minecraft:the_nether	DIM-1
End	minecraft:the_end	DIM1
Mod dimensions	namespace:path	namespace$path

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Known Issues

Issue	Details	Impact
Cave rendering anomalies	Some cave content is inaccurate	Mostly affects Nether; under investigation

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Build

# Build all active platforms (parallel)
./gradlew build -x test --parallel

# Build a single platform
./gradlew :mc-1.21.1:forge:build -x test
./gradlew :mc-1.21.1:fabric:build -x test

# Quick build scripts
scripts/fastbuild/build-all.bat              # All active platforms
scripts/fastbuild/build-forge.bat            # All Forge modules (Gradle 8.9 + JDK 17/21)
scripts/fastbuild/build-fabric-26.1.bat      # Fabric 26.1 (isolated Gradle process)
scripts/fastbuild/build-26.1.bat             # All 26.1 modules

Build artifacts are placed in each platform module's build/libs/ directory.

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License: GPL-3.0

Acknowledgements: Xaero's World Map & Minimap