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How to convert JSON to CSV (and when you shouldn’t)

A practical guide to turning a JSON array of objects into CSV, how nested data is handled, and the edge cases that trip people up.

By The Editorial Team · Reviewed by Engineering · Published 2026-02-10

CSV is the lingua franca of spreadsheets and data imports, but most APIs speak JSON. Converting between them is easy when your JSON is a flat array of objects — and surprisingly subtle when it isn’t.

The ideal shape

CSV is a table: rows and columns. It maps cleanly onto a JSON array where every element is an object with the same keys:

[
  { "name": "Ada", "age": 36 },
  { "name": "Alan", "age": 41 }
]

Each object becomes a row; each key becomes a column. Our converter reads the union of all keys so rows with missing fields still line up.

Nested objects and arrays

CSV has no concept of nesting. When a value is itself an object or array, you have two sensible options:

  • Flatten it first — turn { "a": { "b": 1 } } into an a.b column.
  • Serialize the value as a JSON string inside the cell.

If your data is deeply nested, flatten it before converting so each leaf becomes its own column.

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When not to use CSV

If your data is hierarchical, has repeated groups, or mixes types per field, CSV will lose information. Prefer keeping it as JSON, or convert to a format that preserves structure.

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