JSON Merger

📁

Drop JSON files here

or

You can select multiple files

How to Use

1. Upload JSON files — Drag & drop or click to select multiple files
2. Choose merge mode:
   • Array — Combine all files into a single array [file1, file2, ...]
   • Merge Objects — Combine objects into one { ...file1, ...file2, ... }
   • Concatenate Arrays — Flatten arrays [...file1, ...file2, ...]
3. Download result — Get merged JSON file instantly

Features

✓ Multiple merge modes — Arrays, objects, or array concatenation ✓ Batch processing — Upload dozens of files at once ✓ Property preservation — All data maintained during merge ✓ Conflict handling — Later files override earlier ones (for object merge) ✓ Privacy-first — All processing happens in your browser

Merge Modes

Array Mode (Wrap)

Each file becomes an element in the output array:

Input:

// file1.json
{ "name": "Alice" }

// file2.json
{ "name": "Bob" }

Output:

[
  { "name": "Alice" },
  { "name": "Bob" }
]

Object Merge Mode

Combines all objects into one. Later files override earlier properties:

Input:

// config1.json
{ "apiKey": "abc", "timeout": 5000 }

// config2.json
{ "timeout": 10000, "retries": 3 }

Output:

{
  "apiKey": "abc",
  "timeout": 10000,
  "retries": 3
}

Array Concatenation Mode

Flattens all arrays into a single array:

Input:

// users1.json
[{ "id": 1 }, { "id": 2 }]

// users2.json
[{ "id": 3 }, { "id": 4 }]

Output:

[
  { "id": 1 },
  { "id": 2 },
  { "id": 3 },
  { "id": 4 }
]

Use Cases

Configuration Management

Merge multiple config files (base + environment-specific) into a final configuration.

Data Consolidation

Combine API responses, export files, or database dumps from multiple sources.

Batch Processing

Process multiple JSON exports into a single file for analysis or import.

Testing

Merge test fixtures, mock data, or sample datasets for comprehensive testing.

Data Migration

Combine legacy data files before importing into new systems.

Tips

• File order matters for object merge mode (later files override earlier ones)
• Mixed types: If files contain different JSON types, use Array mode
• Large files: The tool handles large files well, but consider splitting outputs over 100 MB
• Validation: Files are validated before merging — invalid JSON files are skipped

Related Tools

• GeoJSON Merger — Merge GeoJSON FeatureCollections
• TopoJSON Merger — Merge TopoJSON topologies
• JSON Minifier — Reduce merged file size

FAQ

What if files have different structures?

In Array mode, each file becomes an array element regardless of structure. In Object Merge mode, non-object files are skipped with a warning.

Can I merge nested JSON?

Yes! All modes support deeply nested structures. Nesting depth doesn't affect merging.

How are property conflicts handled?

In Object Merge mode, properties from later files override earlier ones. Arrays are replaced, not merged (use Array Concatenation for merging arrays).

Is there a file limit?

No hard limit, but browser memory constraints apply. Most browsers handle 100+ files easily if each is under 10 MB.

Can I merge GeoJSON files?

Yes, but use the GeoJSON Merger instead — it preserves FeatureCollection structure and validates geographic data.