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Convert JSON to CSV Online

Convert JSON arrays or objects into standard RFC 4180 CSV with built-in formula injection protection.

Runs in browser

Drop your .json file here

Up to 10 MiB. Converted privately in your browser.

Choose Files
Max 10 MB per file•Up to 1 files
100% Private — Processed locally in your browser

Conversion Options

How to use Convert JSON to CSV Online

  1. 1

    Upload a JSON file or paste your JSON text.

  2. 2

    Review the auto-detected columns and formula injection safety toggle.

  3. 3

    Download your RFC 4180 compliant CSV file or copy the text.

Safe, private JSON to CSV conversion

Converts JSON arrays of objects or 2D arrays into standard spreadsheet-ready CSV format. Includes built-in spreadsheet formula injection prevention to protect against malicious payloads when opened in Excel or Google Sheets.

What to expect and limitations

Maximum file size: 10 MiB. Maximum nesting depth of 5 levels is flattened automatically (e.g., user.address.city). Unsupported deeply recursive structures are rejected.

Private browser processing

Your data is parsed, validated, and converted entirely in your web browser. File content is never transmitted over the internet to FileNimble servers. All calculations run in your local browser memory. Clearing the tool or leaving the page releases application references; this is not a guarantee of secure memory erasure. Saved downloads remain on your device.

Formula injection prevention is applied by default when generating CSV output to help protect against remote command execution and exfiltration attacks when opening files in spreadsheet applications such as Microsoft Excel and Google Sheets.

Frequently Asked Questions

How does formula injection protection work?

Cell values starting with dangerous formula prefixes (=, +, -, @, \t, \r) are automatically prefixed with a single quote (') to prevent execution when opened in spreadsheet software.

How are nested objects handled?

Nested object keys are flattened using dot notation (for example, person.name), and arrays are represented as JSON strings.

Can I convert large JSON arrays?

Yes, up to 10 MiB of JSON data is safely processed in memory within your browser.

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