CSV to JSON Converter
Transform CSV files or text tables into clean JSON data structures instantly. Everything runs locally in your browser so your data never leaves your device.
How to use
Paste your CSV text into the editor or upload a .csv file using the Upload file button.
Choose your delimiter (or leave on Auto-detect) and configure numeric parsing and unflattening.
Click Convert to JSON to parse rows into structured JSON objects.
Copy the generated JSON to your clipboard or download it as a .json file.
Why convert CSV into JSON?
Comma-separated values (CSV) represent the most ubiquitous format for spreadsheet exports, database dumps, and financial reporting. However, web applications, REST APIs, and modern JavaScript environments operate natively with JavaScript Object Notation (JSON). Converting tabular rows into structured JSON objects enables developers and data engineers to consume spreadsheet data directly in applications, seed test databases, or configure mock API endpoints without manual reformatting.
Automatic data type conversion
By default, raw CSV stores all fields as plain text strings. A standard parser reading a value like 42 or true would preserve them as string literals ("42" and "true"). When Parse numbers is enabled in this tool, the parser automatically identifies numeric values (integers and floats), boolean flags (true and false), and empty cells (null), converting them to their appropriate JSON primitives. This ensures downstream code receives strongly typed properties ready for calculation and logic.
Rebuilding nested hierarchies from flat columns
Flat spreadsheets often represent hierarchical structures using dot-delimited column headers, such as address.city, address.country, or user.profile.bio. The Unflatten keys feature automatically interprets these dot paths and reconstructs deep nested JSON objects. Instead of producing flat keys with dots, the converter builds intuitive nested structures that mirror realistic database models and API payloads.
Strict RFC 4180 parsing and quotation handling
Real-world CSV data frequently contains complex formatting, including commas within addresses or multiline text blocks inside comments. This tool implements strict RFC 4180 parsing compliance, correctly handling double-quoted boundaries, escaped quotation marks (""), and embedded line breaks. It also includes an intelligent delimiter detection engine that automatically discerns standard commas, European semicolons, or tab-separated values (TSV) without manual configuration.
Complete local privacy guarantee
Developer files and exported CSV tables regularly contain proprietary customer information, employee directories, and commercial figures. This converter operates 100% locally inside your browser sandbox using a dedicated Web Worker thread. No rows, cells, or files are uploaded to our server, stored in logs, or exposed to external networks.
Frequently asked questions
Does this tool send my CSV file to any server?
No. The entire conversion process occurs within your local web browser. Your data is never uploaded, tracked, or stored anywhere.
How does automatic delimiter detection work?
The parser inspects the unquoted characters of your first line to determine whether commas, semicolons, tabs, or pipes are the primary separator, ensuring instant compatibility with international CSV variants.
What output formats are supported?
You can output standard Array of Objects (each row is an object keyed by headers), Array of Arrays (a raw 2D grid ideal for matrix computation), or a Keyed Object indexed by the values of the first column.
Can it convert large CSV files without freezing the browser?
Yes. Processing is offloaded to a background Web Worker thread, keeping the user interface completely responsive even when processing multi-megabyte datasets.
How are missing or empty cells handled?
When numeric parsing is enabled, empty cells are cleanly output as null. If numeric parsing is disabled, empty cells remain as empty strings ("").