Convert CSV to JSON, Free and Private

Convert a CSV spreadsheet into JSON in your browser — auto-detects headers and types, ready to paste into code or an API call.

Universal File Converter: Private & Fast

Convert images, videos, audio, and documents directly in your browser. Your files never leave your device, ensuring 100% privacy and security.

Data & Docs Converter

Convert CSV to JSON, or Markdown to HTML completely offline.

Mock Data Generator•JSON Formatter

Drop your file here, or browse

Maximum file size: 50 MB

Supported: CSV, JSON, YAML, XML, TXT, B64, MD, DOCX, XLSX, EPUB

Output format

100% In-Browser Processing

Your files are processed strictly in local device memory. Nothing is uploaded — see how, and check for yourself.

How It Works

How to convert files with DuckConvert

Select Your File

Choose the file you want to convert from your device or drag and drop it into the converter.

Choose Output Format

Select your desired output format and any specific settings for your conversion.

Convert & Download

Click "Start Conversion" and wait for the local process to finish, then download your new file.

Don't take our word for it

This conversion runs entirely in your browser — nothing is uploaded. See exactly how, and check for yourself using your browser's DevTools Network tab.

How It Works

Conversion Mechanics

This is the everyday conversion for developers pulling a spreadsheet export into a script, API payload, or config file — each CSV row becomes one JSON object, keyed by the header row, with numbers and booleans inferred rather than left as strings. It handles quoted fields, embedded commas, and multi-line cells correctly, which is where naive hand-rolled parsers usually break.

Why It's Private

Runs Entirely In Your Browser: Files are decoded and re-encoded strictly in local memory.
No Network Requests: The converter makes no calls to any server — check your browser's DevTools Network tab to confirm.
Nothing to Sign Up For: No account, no upload, and no server-side storage of your files.
Runs On Your Hardware: Processing uses your own device's CPU via Web Workers, not a remote server.

Step-by-Step CSV to JSON Local Guide

Select File

Drop your .csv file into the box above.

Configure

Confirm JSON is selected as the output format.

Convert

Click Convert — parsing happens locally in your browser.

Save Result

Download the resulting .json file.

Frequently Asked Questions on Secure CSV to JSON Conversion

Yes — the first row's values become the JSON object keys for every subsequent row.

Values that look like numbers or booleans are converted to actual JSON numbers/booleans rather than left as quoted strings, unless they're quoted in the source CSV.

Yes, though very large files (hundreds of thousands of rows) will take longer since parsing runs on your device rather than a server.