JSON Flattener Free Online Tool 2026

Last updated March 22, 2026

Example: Deep Nesting

// Input (5 levels deep):
{
  "a": {
    "b": {
      "c": {
        "d": {
          "e": "deep value"
        }
      }
    }
  }
}

// Output:
{
  "a.b.c.d.e": "deep value"
}

Example: Array Flattening with Bracket Notation

// Input:
{
  "order": {
    "id": "ORD-001",
    "items": [
      { "product": "Widget", "qty": 2, "price": 10.00 },
      { "product": "Gadget", "qty": 1, "price": 25.00 }
    ]
  }
}

// Output (bracket notation for arrays):
{
  "order.id": "ORD-001",
  "order.items[0].product": "Widget",
  "order.items[0].qty": 2,
  "order.items[0].price": 10.00,
  "order.items[1].product": "Gadget",
  "order.items[1].qty": 1,
  "order.items[1].price": 25.00
}

Example: API Response Flattening

// Input (GitHub API user response):
{
  "login": "octocat",
  "id": 1,
  "name": "The Octocat",
  "company": "GitHub",
  "location": "San Francisco, CA",
  "public_repos": 8,
  "followers": 20000,
  "plan": {
    "name": "pro",
    "space": 976562499,
    "private_repos": 9999
  }
}

// Output (flattened):
{
  "login": "octocat",
  "id": 1,
  "name": "The Octocat",
  "company": "GitHub",
  "location": "San Francisco, CA",
  "public_repos": 8,
  "followers": 20000,
  "plan.name": "pro",
  "plan.space": 976562499,
  "plan.private_repos": 9999
}

Key Separator Options

// Same nested object with different separator styles:
Input: { "user": { "first_name": "Alice" } }

Dot notation (default):
  "user.first_name": "Alice"

Underscore notation:
  "user_first_name": "Alice"

Bracket notation:
  "user[first_name]": "Alice"

Double underscore:
  "user__first_name": "Alice"

Example: CSV Export After Flattening

// Input JSON array:
[
  { "name": "Alice", "address": { "city": "New York", "zip": "10001" } },
  { "name": "Bob",   "address": { "city": "Chicago",  "zip": "60601" } },
  { "name": "Carol", "address": { "city": "Austin",   "zip": "73301" } }
]

// Flattened:
[
  { "name": "Alice", "address.city": "New York", "address.zip": "10001" },
  { "name": "Bob",   "address.city": "Chicago",  "address.zip": "60601" },
  { "name": "Carol", "address.city": "Austin",   "address.zip": "73301" }
]

// CSV export:
name,address.city,address.zip
Alice,New York,10001
Bob,Chicago,60601
Carol,Austin,73301

Example: Unflattening (Reverse Operation)

// Input (flat key-value pairs):
{
  "database.host": "localhost",
  "database.port": 5432,
  "database.credentials.user": "admin",
  "database.credentials.password": "secret",
  "server.port": 8080,
  "server.debug": true
}

// Output (unflattened / nested):
{
  "database": {
    "host": "localhost",
    "port": 5432,
    "credentials": {
      "user": "admin",
      "password": "secret"
    }
  },
  "server": {
    "port": 8080,
    "debug": true
  }
}

Flattening Statistics

Input JSON:
  Original keys:    8
  Max nesting depth: 4
  Arrays found:     2 (with 5 total items)

Output (flattened):
  Flattened keys:   23
  Key expansion:    +15 keys (from array flattening)
  
Schema inference:
  string fields:    12
  number fields:     8
  boolean fields:    2
  null fields:       1

Null Value Handling

// Input:
{
  "user": {
    "name": "Alice",
    "middleName": null,
    "age": 30
  }
}

// Output (null preserved):
{
  "user.name": "Alice",
  "user.middleName": null,
  "user.age": 30
}

// CSV output (null as empty cell):
user.name,user.middleName,user.age
Alice,,30

Paste your nested JSON to flatten it into dot-notation key-value pairs. Use the CSV export to open the data directly in Excel or Google Sheets.

// Input (nested):
{
  "user": {
    "name": "Alice",
    "age": 30,
    "address": {
      "city": "New York",
      "zip": "10001",
      "country": "US"
    }
  }
}

// Output (flattened with dot notation):
{
  "user.name": "Alice",
  "user.age": 30,
  "user.address.city": "New York",
  "user.address.zip": "10001",
  "user.address.country": "US"
}