TopoJSON Splitter

Split TopoJSON topology files into multiple separate files by object or property, while preserving the efficient arc topology structure.

How to Use

1. Upload TopoJSON file or paste data
2. Choose split method:
   • By object (e.g., countries, states, cities)
   • By property within objects (e.g., country code, admin level)
3. Preview split — See resulting file structure
4. Download all files as ZIP

Features

✓ Split by object — Separate each TopoJSON object into its own file
✓ Split by property — Group features by property value
✓ Preserve topology — Maintains arc sharing and compression
✓ Smart re-topology — Rebuilds arc references for each split
✓ Property detection — Auto-detects available properties
✓ Batch download — Get all files as ZIP archive

Use Cases

🗺️ Extract countries — Split world topology into individual country files
🏛️ Separate layers — Extract different object types (boundaries, rivers, roads)
📊 Regional datasets — Create topology files for specific regions
🎯 Reduce file size — Split large topologies into manageable pieces
🔍 Targeted analysis — Work with specific geographic areas

TopoJSON Structure

TopoJSON files contain multiple named objects:

{
  "type": "Topology",
  "objects": {
    "countries": { ... },
    "states": { ... },
    "cities": { ... }
  },
  "arcs": [ ... ]
}

Split Methods

1. Split by Object

Creates one file per object in the topology.

Example Input:

{
  "objects": {
    "countries": { ... },
    "states": { ... }
  }
}

Output:

• countries.topojson
• states.topojson

2. Split by Property

Splits features within an object by property value.

Example: Split countries object by ISO code
Output: One file per country

Tips

💡 Use object split for different layer types (countries, rivers, etc.)
💡 Use property split for extracting individual features
💡 Preview topology to understand arc count and file sizes
💡 Maintain arc efficiency by keeping related features together
💡 Check quantization — Topology precision may affect splits

Technical Details

Input Format

• Valid TopoJSON Topology
• Must contain objects and arcs
• Supports all geometry types

Output Format

• Individual TopoJSON files with reconstructed topology
• Shared arcs are duplicated in each output file
• ZIP archive containing all files

Arc Handling

• Arcs referenced by features are included in output
• Unreferenced arcs are removed
• Arc indices are recomputed for each file

Limitations

• Splitting breaks shared topology (arcs duplicated)
• File size may increase after splitting
• Large topologies may take time to process

Related Tools

• GeoJSON Splitter — Split GeoJSON files
• TopoJSON Merger — Merge TopoJSON files
• GeoJSON ↔ TopoJSON — Convert formats

Frequently Asked Questions

Q: Will splitting increase file size?
A: Yes, because shared arcs are duplicated across files. The topology efficiency is partially lost.

Q: Can I split a single object by property?
A: Yes! Select the object, then choose property split method.

Q: What happens to shared arcs between features?
A: Arcs are duplicated in each output file that needs them.

Q: How do filenames work?
A: For object split: object name. For property split: property value (sanitized).

Q: Can I merge the split files back together?
A: Yes, use the TopoJSON Merger, but note that shared topology won't be automatically restored.

Q: What if features don't have the split property?
A: They're grouped into an "undefined.topojson" file.

Q: Does this preserve quantization and transforms?
A: Yes, all topology parameters are preserved in output files.

Q: Can I split very large topology files?
A: Yes, but processing time increases with arc count. Files >50MB may be slow.