JSON Merge

Combine multiple JSON objects with smart conflict resolution. Deep merge nested objects, handle arrays, and customize merge behavior for your workflow.

All merging happens locally in your browser. Your data never leaves your device.
Merge Options

JSON Sources (2)

Drag to reorder • Top to bottom priority
1
2

No merge result yet

Add valid JSON to your sources to see the merged result

How Merging Works & Tips

Merge Rules

  • • Objects: Properties from later sources override earlier ones
  • • Deep merge: Nested objects are recursively merged
  • • Arrays: Choose replace, concat, unique, or merge by key
  • • Order: Sources are merged top to bottom (drag to reorder)

Keyboard Shortcuts

  • Ctrl+Enter — Merge sources
  • Ctrl+S — Download result

RFC 7396 Merge Patch

The merge patch shows changes from Source 1 to the result. Use null values to delete keys.

How to Use

  1. 1Paste, upload, or drag & drop your first JSON object. Name your sources for clarity.
  2. 2Add more sources as needed. Use "Batch Upload" for multiple files at once.
  3. 3Drag sources to reorder them — merge priority goes from top to bottom.
  4. 4Configure merge options: array handling, null values, output format, and key sorting.
  5. 5View the result in Code, Tree, or Diff view. Download or generate an RFC 7396 Merge Patch.

Array Merge Strategies

  • Replace: Later sources completely override earlier arrays
  • Concatenate: Arrays are combined end-to-end
  • Unique: Array values are merged, removing duplicates
  • Merge by Key: Objects in arrays are matched and merged by a key field (e.g., id)

Keyboard Shortcuts

  • Ctrl + Enter — Merge sources
  • Ctrl + S — Download result

Frequently Asked Questions

What is JSON merging?

JSON merging combines two or more JSON objects into a single unified object. When objects have overlapping keys, a merge strategy determines which value wins. Deep merging recursively combines nested objects rather than replacing them entirely.

How does deep merge differ from shallow merge?

Shallow merge only combines top-level properties — if both objects have the same key, the second value completely replaces the first. Deep merge recursively combines nested objects, preserving properties that exist in one object but not the other.

What happens when both JSON objects have the same key?

By default, the value from the later source wins (last-write-wins). For arrays, you can choose to replace, concatenate, merge unique values, or merge by a key field (like "id"). For nested objects with deep merge enabled, the objects are recursively combined.

Can I merge more than two JSON files?

Yes! You can add as many JSON sources as needed using the "Add Another JSON Source" button or batch upload multiple files at once. Sources are merged in order from top to bottom, and you can drag to reorder them.

Is my data safe when using this tool?

Absolutely. All merging happens entirely in your browser using JavaScript. Your JSON data is never sent to any server, stored, or logged. This tool is completely privacy-first.

What is a JSON Merge Patch (RFC 7396)?

RFC 7396 defines a standard format for describing changes to a JSON document. This tool can generate a merge patch that shows what changed from your first source to the merged result. Use it with HTTP PATCH requests or to track changes programmatically.

How does "Merge by Key" work for arrays?

When you select "Merge by key field", arrays of objects are intelligently merged based on a matching key (like "id"). Objects with the same key value are deep-merged together, while new objects are added. This is perfect for merging user lists, product catalogs, or any array where items have unique identifiers.

What are common use cases for JSON merging?

Common use cases include: combining configuration files (like package.json), merging API responses, consolidating data exports, creating unified settings from defaults and overrides, merging i18n/translation files, and aggregating multiple JSON data sources.

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