CSV to JSON Converter — Free Online CSV ⇄ JSON Tool

Convert CSV to JSON and JSON to CSV instantly. Supports comma, tab, pipe, and custom delimiters with header-row detection — all processed locally in your browser. This free online CSV to JSON converter runs entirely in your browser — no data is ever uploaded to a server.

About this tool

CSV (Comma-Separated Values) is one of the oldest and most widely supported data formats, used by spreadsheets, databases, and data science tools. JSON (JavaScript Object Notation) is the standard format for web APIs and modern application development. This tool converts between CSV and JSON formats with support for multiple delimiters (comma, tab, pipe, semicolon, or custom), configurable header rows, and drag-and-drop file uploads for seamless data transformation.

The conversion is bidirectional: you can convert CSV spreadsheets into structured JSON arrays for use in web applications, or convert JSON data back into CSV for analysis in spreadsheet software like Excel or Google Sheets. The delimiter option is particularly useful when working with regional CSV variations — European CSV files often use semicolons instead of commas, and TSV (tab-separated values) is common in data science workflows.

Common Use Cases

  • Importing spreadsheet data from Excel or Google Sheets into web applications as JSON
  • Converting database exports between relational (tabular CSV) and document-oriented (JSON) formats
  • Preparing CSV datasets for machine learning pipelines that require JSON input
  • Transforming API response data (JSON) into CSV for reporting and business analysis
  • Migrating data between systems that use different data interchange formats
  • Working with TSV and semicolon-delimited regional CSV variants

Pro Tips

  • Enable "First row as headers" to convert CSV columns into meaningful JSON property names
  • Use the tab delimiter for TSV files common in data science — it avoids issues with commas in data
  • Check that your CSV uses consistent quoting for fields containing the delimiter character
  • When converting JSON to CSV, ensure the JSON is an array of objects with consistent keys

Frequently Asked Questions

What is the difference between CSV and JSON?

CSV stores data in a tabular format where each line is a row and values are separated by delimiters. JSON stores data as key-value pairs and supports nested structures. CSV is better for spreadsheets and large datasets, while JSON is better for hierarchical data and web APIs.

Why does my CSV not convert correctly?

Common issues include: incorrect delimiter selection, inconsistent quoting, missing headers, or encoding problems. Try switching between delimiters (comma, tab, semicolon) and check that your CSV follows RFC 4180 standards.

Can I convert CSV files with commas inside quoted fields?

Yes. The tool respects RFC 4180 quoting rules. If a field contains the delimiter, it should be enclosed in double quotes. For example: "Smith, John", 42, "Boston, MA"

What is the maximum file size supported?

The tool processes data in your browser and does not upload files to any server. Performance depends on your device, but typical CSV files up to several megabytes should convert quickly.

How to Use

1. Enter your input — type or paste your csv or JSON data and choose your delimiter.

2. See live results — the tool updates instantly as you type.

3. Copy or download — copy the output to clipboard or download it.

4. History — your recent inputs are saved locally and can be pinned for quick access.

Example

Paste "name,age\nalice,30\nbob,25" and click Convert — you get JSON [{name:alice,age:30},{name:bob,age:25}]. Flip to JSON-to-CSV to go the other way, or switch the delimiter to tab or pipe.

Also check out the live tool at freeq.one/tools/csv — part of the FreeQ.One suite of free online tools.