JSON Unflatten

What is JSON Unflatten

Last reviewed: April 18, 2026

JSON (JavaScript Object Notation) is a lightweight, human-readable data format used almost everywhere on the web for APIs, config files, and log output.

JSON Unflatten takes a flat map like `{ "user.id": 1, "user.tags[0]": "admin" }` and rebuilds the original nested object structure.

Pair it with JSON Flatten for lossless round-trips between nested and flat representations.

Why use it

• Restore structure after KV-store hydration.
• Rebuild JSON from dotted-config files.
• Merge flat diff outputs back to nested form.
• Teach path-based JSON navigation.
• Undo a JSON Flatten transformation.

Features

• Inverse of JSON Flatten
• Handles nested objects + arrays
• Custom separator
• Configurable round-trip
• Zero-upload JSON Unflatten pipeline, nothing touches a server

How to use JSON Unflatten

1. Paste flat JSON. Dotted / bracketed keys.
2. Match separator. Use the same separator as when flattening.
3. Run. Copy the rebuilt nested JSON.

Example (before/after)

{
  "user.id": 1,
  "user.tags[0]": "admin",
  "user.tags[1]": "ops"
}

{
  "user": {
    "id": 1,
    "tags": ["admin", "ops"]
  }
}

Common errors

FAQ

Related tools

Pair with JSON Flatten and diff tools. You can also browse the full Data Converters category for more options.