How to Convert Nested JSON to CSV (With Examples)

What is nested JSON?

Nested JSON is JSON where values are themselves objects or arrays — creating a tree structure rather than a flat key-value map.

{
  "user": {
    "name": "Alice",
    "address": {
      "city": "London",
      "country": "UK"
    }
  },
  "active": true
}

Flat JSON tools struggle with this — they either skip the nested data or error out.

How JSONtoCSV.tools handles nested JSON

The converter automatically flattens nested objects using dot notation:

Each level of nesting is joined with the separator character. You can change the separator to underscore or any other character in the Options tab.

Arrays inside JSON objects

When a key's value is an array, you have two options:

**Option 1: Index expansion** — each array item becomes its own column: `tags.0`, `tags.1`, `tags.2`

**Option 2: Expand arrays to text** — items are joined into one cell: `"typescript | react | nodejs"`

**Option 3: Stringify** — the array is stored as a JSON string: `["typescript","react","nodejs"]`

Tips for nested JSON conversion

• →Use dot notation for human-readable column names
• →Use underscore notation if your downstream tool can't handle dots in headers
• →Enable "Stringify nested" when you want to preserve nested structure for later parsing
• →Use "Include only" in the Options tab to cherry-pick specific nested fields