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Convert CSV and JSON tables

All cells stay strings. Maximum input: 100,000 UTF-16 units / 400,000 UTF-8 bytes; 2,000 rows including headers, 200 columns and 20,000 cells.

Table options

On: JSON array of objects with unique nonempty keys. Off: JSON array of string arrays. Rows must have consistent columns; JSON cells must be strings. A header-only CSV becomes []; its header names cannot be restored from that empty array.

Paste a table.

The table stays on this page. No upload or saved history.

Help & FAQs

Paste your table, choose the direction and convert the actual content.

How to convert a table

  1. Choose CSV to JSON or JSON to CSV, then paste the input.
  2. Set the delimiter and whether the first CSV row contains headers. For JSON, use only string values.
  3. Convert, review the result and any formula-text prefixes, then copy or download the real file.

A clear table contract

CSV supports commas, semicolons or tabs, quoted fields, doubled quotes and multiline fields. Records may use CRLF, LF or CR; exported CSV uses CRLF. A leading BOM is accepted. Header mode uses a JSON array of objects with nonempty unique field names and the same fields in each object; otherwise use an array of string arrays. All cell values must be strings: numbers, booleans, null and nested values are rejected.

Input is limited to 100,000 UTF-16 units / 400,000 UTF-8 bytes, 2,000 rows including the header, 200 columns and 20,000 cells. Output is limited to 300,000 units / 500,000 bytes, with a 45-second processing budget. Processing and results stay on this page.

Common questions

Will long IDs or leading zeroes change?

No. All cell values remain strings, including 9007199254740993 and 0012. JSON numbers are rejected instead of being rounded or silently converted.

Why are some CSV cells prefixed with an apostrophe?

The default formula-text option prefixes cells beginning with tab/line breaks or formula markers = + - @ after ASCII whitespace, including headers. This changes cell text. Turn it off to preserve the original; spreadsheet behavior varies, so this is not a universal safety guarantee.

What happens to duplicate headers or object keys?

They are rejected. Each row must have the same width, and each object must have the same unique fields. JSON object key order follows the first record. CSV does not retain JSON formatting or type information.