JSON Flatten

Flatten nested JSON objects to dot-notation keys and unflatten them back. Works with deeply nested objects and arrays.

Input

Output

How to Use JSON Flatten

Paste Your JSON

Paste any deeply nested JSON object or array into the input panel.

Choose Direction

Click "Flatten" to convert nested objects into flat dot-notation keys like "user.address.city". Click "Unflatten" to expand flat key-path objects back into nested JSON.

Copy the Result

The output appears on the right. Use the Copy button to grab it.

Examples

Before (Nested JSON)

{
  "user": {
    "name": "John",
    "address": {
      "city": "New York",
      "zip": "10001"
    }
  },
  "tags": ["admin", "editor"]
}

After (Flattened)

{
  "user.name": "John",
  "user.address.city": "New York",
  "user.address.zip": "10001",
  "tags[0]": "admin",
  "tags[1]": "editor"
}

Frequently Asked Questions

What does flattening JSON do?

Flattening converts nested JSON like {"user":{"name":"John","address":{"city":"NYC"}}} into a flat object with dot-notation keys: {"user.name":"John","user.address.city":"NYC"}. This is useful for CSV export, database inserts, and searching for values by key path.

How are arrays handled?

Array elements are flattened with bracket notation: "items[0].name", "items[1].name", etc. This preserves the index and structure of your arrays.

Can I flatten in both directions?

Yes. The Unflatten button takes a flat object with dot-notation keys and restores the original nested structure. This is useful when you get data in flat format (like from a CSV or a key-value store) and need to reconstruct the original JSON.

When to Flatten JSON

Flattening JSON is a practical technique when you need to bridge between nested data structures and flat storage systems. If you're inserting API data into a SQL database, a flat list of column→value pairs is much easier to work with than nested objects.

It's also handy for debugging — searching for "user.address.city" in a flat map is straightforward, while finding the same value in a 5-level deep nested object requires manually expanding each level. Some logging and monitoring systems (like Elasticsearch) use dot-notation keys internally for this reason.

The reverse (unflattening) is useful when you're loading data from a CSV or a key-value database back into an application that expects nested JSON. For example, environment variables like DB_HOST and DB_PORT can be unflattened into {"db": {"host": "...", "port": "..."}}.

Guide

JSON Structure Guide

Flattening, tree views, and working with nested JSON.