Web Tools
JSON Merge Tool
Deep merge two JSON objects with configurable array strategies. Supports replace, concat, and union modes for arrays. Runs entirely in your browser — your data never leaves your machine.
json merge deep-merge config combine
Published May 30, 2026
All interactive tools run entirely in your browser. Your data never leaves your device.
How It Works
Paste a base JSON document and a patch JSON document. The tool deep-merges the patch into the base, recursively combining nested objects while letting you choose how arrays are handled.
Features
- Deep merge: recursively merges nested objects
- Array strategy — Replace: patch array completely replaces base array
- Array strategy — Concat: appends patch array items after base array items
- Array strategy — Union: merges arrays without duplicates (deep equality)
- Type flexibility: handles objects, arrays, strings, numbers, booleans, null
- Pretty output: configurable indentation (2 spaces default)
- Error reporting: clear messages for invalid JSON
- 5 examples: simple merge, nested merge, array concat, array union, package.json merge
- Private: runs entirely in the browser — no data transmitted
Use Cases
- Merging configuration files (package.json, tsconfig, etc.)
- Combining API responses or data payloads
- Creating configuration overrides for different environments
- Previewing the result of deep-merging two objects before writing code