What is CSV and how does it differ from JSON?

CSV (Comma-Separated Values) is a tabular plain-text format where each row is a record and columns are separated by a delimiter (usually a comma). JSON (JavaScript Object Notation) is a structured data format using key-value pairs and arrays. CSV is compact and great for spreadsheets; JSON is more flexible and widely used in APIs and web applications.

Does the converter support custom delimiters?

Yes. When converting CSV to JSON, you can choose between Comma (,), Semicolon (;), Tab, and Pipe (|) delimiters. This covers the vast majority of real-world CSV variants including European CSV files that use semicolons, TSV (tab-separated) exports from Excel, and pipe-delimited database dumps.

Does it use the first row as column headers?

Yes. The converter treats the first row of your CSV as the header row and uses those values as JSON object keys. Every subsequent row becomes a JSON object in the output array. Make sure your CSV has a clean, consistent header row for best results.

What format does the JSON input need to be in for JSON to CSV?

The JSON input must be an array of objects, where each object has the same keys. For example: [{"name":"Alice","age":30},{"name":"Bob","age":25}]. The keys of the first object become the CSV header row. Mixed arrays or nested objects are not fully supported - flatten nested data before converting.

Is there a file size limit?

There is no hard limit imposed by this tool. All processing happens in your browser, so practical limits depend on your device memory. For very large files (hundreds of MB), consider using a command-line tool like jq or csvkit instead.

Yes. All conversion is done entirely in your browser using JavaScript. No data is ever uploaded or sent to any server. The tool works completely offline once the page has loaded.

CSV to JSON Converter

Convert CSV to JSON and JSON to CSV online. Free CSV-JSON converter - supports headers, custom delimiters, and pretty print.

🔒 Your text stays in your browser - nothing is sent to our servers

Delimiter:

CSV Input

JSON Output

How to Use

Three steps to get started

Choose direction

Select "CSV → JSON" to convert a CSV file, or "JSON → CSV" to export JSON data as a spreadsheet.

Paste your data

Paste your CSV or JSON into the input area. For CSV, select the correct delimiter if it is not a comma.

Copy the result

Click Copy to grab the converted output and use it in your application, database, or spreadsheet tool.

About This Tool

CSV to JSON conversion explained

CSV (Comma-Separated Values, described by RFC 4180) is a flat, tabular text format: one record per line, fields separated by a delimiter, and an optional header row naming the columns. JSON (RFC 8259) is a hierarchical format built from objects and arrays. Converting CSV to JSON therefore means turning a rectangle into an array of objects, where the header row supplies the keys and each data row becomes one object. Converting back flattens that array into rows, taking the keys of the first object as the header.

Converting between them is a daily task for developers and data analysts:

API preparation: Export from Google Sheets or Excel as CSV, then convert to JSON to POST to a REST endpoint or load as a test fixture
Analysis: Take a JSON API response and convert to CSV so it opens in Excel, Numbers, Tableau, or a pandas read_csv call
Database seeding: Turn a CSV dump into the array-of-documents shape MongoDB's insertMany or a Firebase import expects
ETL and migration: Bridge two systems whose importers and exporters disagree about format
Static sites and dashboards: Convert a spreadsheet of content into a JSON file a front end can fetch directly

Why CSV conversion goes wrong

CSV looks trivial and is not. The format was in wide use for decades before RFC 4180 attempted to describe it in 2005, and real files still disagree on the details. The recurring problems:

Delimiters inside data. A field like Smith, John must be wrapped in double quotes, and a literal quote inside a quoted field is escaped by doubling it (""). This tool handles both.
Locale variance. Excel exports semicolon-delimited files in locales where the comma is the decimal separator, which is why the delimiter selector offers semicolon, tab, and pipe alongside comma.
Type loss. CSV has no types - every cell is text. A ZIP code like 02134 or a long ID can lose its leading zeros or be reinterpreted as a number when it round-trips through a spreadsheet.
Nesting. JSON objects can contain other objects and arrays; CSV cannot represent that. Flatten nested data (for example to address.city columns) before converting JSON to CSV.
Line endings and BOM. RFC 4180 specifies CRLF, files from Unix tools use LF, and Excel prepends a UTF-8 byte-order mark that can turn the first header into a key with an invisible prefix.

JSON output is pretty-printed with two-space indentation so it is readable and diff-friendly. Everything is parsed and serialised by JavaScript in this browser tab - customer lists, exports, and internal datasets are never uploaded, and the only size limit is your device's available memory.

FAQ

Frequently Asked Questions

Related Tools