JSON to CSV Converter
Handle Million Rows in Your Browser

Convert JSON files to CSV format instantly in your browser. Paste JSON text directly or upload a .json file. Powered by DuckDB-WASM, no server upload required.

Drag & drop your file here, or browse

Accepts: .json (up to 500 MB)

Your data stays in your browser. By using this tool, you agree to our Terms and Privacy Policy.

How to Convert JSON to CSV

Choose the "Upload File" tab and drag & drop your .json file, or switch to the "Paste Text" tab and paste your JSON data directly.

The tool reads your JSON using DuckDB-WASM. Supported formats: Array of objects ([{...}, {...}]) and NDJSON (one object per line).

Preview the CSV output with column headers and row data.

Click the download button to save the CSV file.

Features

100% Browser-Based: Your data never leaves your device. All conversion happens locally using WebAssembly — no server upload, no privacy concerns.
Paste or Upload: Paste JSON directly into the text area or upload a .json file. Perfect for quick tests or batch conversions.
Large File Support: Powered by DuckDB-WASM, this tool handles large JSON files (up to 500MB) efficiently in your browser.

JSON vs CSV: What's the Difference?

JSON (JavaScript Object Notation) represents data as key-value pairs, supporting nested structures and distinct data types. CSV (Comma-Separated Values) is a simple tabular format widely compatible with Excel, databases, and data pipelines.

	JSON	CSV
Structure	Key-value pairs (nestable)	Flat table (rows × columns)
Data types	Strings, numbers, booleans, null	Everything is a string
Readability	Easy to consume in code	Easy to view in spreadsheets
File size	Larger (key names repeated per row)	Compact
Common use	Web APIs, config files, NoSQL	Data exchange, Excel, data pipelines

Benefits of Converting JSON to CSV

Opens instantly in Excel and spreadsheets — easy to review and share data
Data pipeline integration — most ETL tools, databases, and data science frameworks import CSV natively
Smaller file size — CSV doesn't repeat column names for every row, resulting in more compact output

Frequently Asked Questions

Is my data uploaded to a server?

No. Your file never leaves your browser. All processing happens locally using WebAssembly. No data is sent to any server.

Is it free?

Yes, this tool is completely free with no row limits.

What JSON structures are supported?

This tool supports JSON arrays of objects (e.g., [{"id": 1}, {"id": 2}]) and NDJSON (newline-delimited JSON). Each object becomes a row, and keys become column headers. Wrapper objects like {"data": [...]} are not supported — extract the inner array first.

Can I convert a large JSON file with millions of rows to CSV?

Yes. This tool uses DuckDB-WASM to process files entirely in your browser. It can handle millions of rows without crashing or uploading your data, and supports large files depending on your device's available memory. Files over 150MB automatically switch to "stable processing mode," which writes the output directly to disk to avoid browser memory pressure.

Can I paste JSON directly instead of uploading a file?

Yes. Switch to the "Paste Text" tab and paste your JSON data directly. The tool validates and converts it instantly. For pasted text, the limit is 10MB — use file upload for larger data.

What is the file size limit?

The input limit is 500MB for file upload. For pasted text, the limit is 10MB. CSV output is typically smaller than the JSON input since column names are not repeated for every row.

What is NDJSON?

NDJSON (Newline Delimited JSON) is a format where each line contains a single JSON object. It's commonly used for log files and streaming data. Example: {"id": 1}\n{"id": 2}. This tool converts NDJSON to CSV just like a regular JSON array.

Can I remove columns or filter data before converting?

This page is a dedicated conversion tool. If you need to remove unnecessary columns, filter data by conditions, or merge multiple files before converting, try the data analysis platform LeapRows. No account required — start using it right in your browser.

Can I use this on a smartphone or tablet?

Yes, it works on any device with a modern browser. However, for large file processing and easier file management after download, we strongly recommend using a desktop or laptop computer.

What browsers are supported?

Any modern browser that supports WebAssembly: Chrome, Firefox, Edge, Safari (14+). Chrome is recommended for best performance with large files.