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JSON to CSV Table – Flatten Nested Objects Online

Converter Data converter CSV JSON table
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JSON to CSV Table – Flatten Nested Objects

Paste nested JSON, instantly flatten objects, preview as table & export to CSV

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JSON Input
Flattened Table & CSV
📋 Table Preview
No data yet. Paste JSON and click Flatten & Convert.

Frequently Asked Questions

What is JSON flattening?

JSON flattening is the process of converting nested JSON objects into a flat, single-level structure. Nested keys are joined using a separator (like a dot), so {"user":{"name":"John"}} becomes {"user.name":"John"}. This makes the data compatible with tabular formats like CSV and spreadsheet applications.

How are nested arrays handled?

When a field contains a nested array, this tool serializes it as a JSON string so it fits into a single table cell. For example, ["red","blue"] becomes the string ["red","blue"] in the CSV. This prevents unexpected row multiplication while preserving all data.

Is the CSV compatible with Microsoft Excel?

Yes. Downloaded CSV files include a UTF-8 BOM (Byte Order Mark) so Excel can correctly interpret special characters, accented letters, and non-Latin scripts. Fields containing commas, quotes, or line breaks are properly escaped according to RFC 4180.

What if my JSON objects have inconsistent keys?

The tool automatically collects all unique key paths across every object in your array. If a particular object is missing a key that others have, that cell is simply left empty. This ensures no data is lost even with irregular JSON structures.

Can I convert a single JSON object (not an array)?

Absolutely. If you paste a single JSON object like {"name":"Alice","age":30}, the tool automatically wraps it into a one-row table. The same flattening logic applies to any nested fields within that object.

What separator should I use for nested keys?

The default is a dot (.), producing keys like address.city. You can switch to underscore (_), double underscore (__), or arrow ( > ) depending on your needs. Underscores are popular for database column names and SQL imports.

Is my data sent to a server?

No. All processing happens entirely in your browser using client-side JavaScript. Your JSON data never leaves your device. This means the tool works offline, is fast, and your sensitive data remains completely private.

What's the maximum JSON size I can process?

Since processing is done in-browser, the practical limit depends on your device's memory and browser performance. Most modern browsers handle JSON arrays with thousands of objects and dozens of columns without issue. For very large datasets (100k+ rows), consider using a dedicated data processing tool.

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