About The JSON Flattener

JSON Flattener converts nested JSON into flat path-key JSON, and can rebuild flat path maps back into nested JSON. It is useful for CSV exports, analytics pipelines, field mapping, and quick payload inspection.

The tool runs locally in your browser. Flatten mode includes array positions in the path, and unflatten mode uses the selected delimiter to rebuild nested objects and arrays.

How to Flatten JSON Online

1. Choose Flatten or Unflatten.
2. Set the path delimiter, such as ..
3. Paste valid JSON into JSON input.
4. Click Run JSON Tool.
5. Review and copy the generated JSON result.

Choosing Options Correctly

Flatten:
Use this to turn nested data into keys such as user.roles.0.name.

Unflatten:
Use this when your input is already a JSON object whose keys contain path delimiters.

Common Use Cases

• Preparing nested JSON for spreadsheet or CSV workflows.
• Building path maps for ETL configuration.
• Inspecting nested API responses quickly.
• Rebuilding simple flattened payloads for testing.

Quick FAQ

Why did parsing fail?
The input is not valid JSON, or it includes JavaScript-only syntax such as comments or trailing commas.

Can delimiter characters inside keys cause issues?
Yes. If a key already contains the chosen delimiter, flattened paths can become ambiguous.

Is my JSON uploaded?
No. Flattening is designed to run in the browser.

Can arrays be flattened?
Yes, but array indexes become part of the path. That may or may not fit the target system.