How to Flatten Nested JSON for CSV Export

CSV is a flat grid of rows and columns. JSON can nest objects and arrays arbitrarily deep. Bridging that gap is the hard part of JSON to CSV conversion.

The problem

{
  "name": "Alice",
  "address": { "city": "Paris", "zip": "75001" }
}

A flat CSV can't hold address as a cell. You have to decide how to represent it.

Strategy 1: dot-notation columns

Flatten nested keys into compound column names:

name,address.city,address.zip
Alice,Paris,75001

This keeps every value in its own column and is the most spreadsheet-friendly approach.

Strategy 2: serialize the nested value

Store the nested object as a JSON string in one cell:

name,address
Alice,"{""city"":""Paris"",""zip"":""75001""}"

Compact, but the cell is no longer easy to read or sort.

Handling arrays

Arrays are trickier. Options:

• Join simple arrays into one cell: "red; green; blue".
• Explode into multiple rows (one row per array item), repeating the parent fields.
• Index into columns: tags.0, tags.1.

Pick based on whether you need to filter/sort those values in the spreadsheet.

Tip

Before flattening, make sure the JSON is valid — run it through the config validator. Then convert with the JSON to CSV tool.