CSV ⇄ JSON Converter

How to use the CSV ⇄ JSON Converter

1. Pick a direction: CSV → JSON or JSON → CSV.
2. Paste your data or click Open file. Conversion happens as you type.
3. For CSV, leave the delimiter on Auto-detect or choose comma, semicolon, tab or pipe. Untick First row is headers if your file has no header row.
4. Turn Detect numbers off if you need every value kept as text, for example ZIP codes or IDs with leading zeros (those are kept as text anyway).
5. For JSON → CSV, nested objects become columns like address.city. Choose how lists inside items should be written.
6. Check the preview table, then copy the result or download it as a file.

How it works

The CSV reader follows RFC 4180, the common definition of the format. Fields are separated by a delimiter, and any field can be wrapped in double quotes. Inside quotes, a delimiter or even a line break is part of the value, and a quote is written twice (""). So the line "Lopez, Sam","She said ""hi""" holds two values: Lopez, Sam and She said "hi". Windows (CRLF), Unix (LF) and old Mac (CR) line endings all work, and a byte-order mark at the start of the file is ignored.

Auto-detect tries comma, semicolon, tab and pipe on the first rows and picks the one that splits them into the same number of columns most consistently. Semicolons are common in countries that use a decimal comma. With type detection on, plain numbers like 36 or -2.5 become JSON numbers, true/false become booleans, and empty cells become null. Values such as 00742 or numbers too large to store exactly stay as text so nothing is lost.

Going the other way, each object becomes a row and every key found in any object becomes a column, in the order first seen. Nested objects are flattened with dots, so {"address":{"city":"Denver"}} produces a column address.city. Values that contain the delimiter, quotes, line breaks or leading spaces are quoted automatically. The formula-protection option puts an apostrophe in front of cells starting with =, +, - or @, which stops spreadsheet programs from running them as formulas when you open data from an unknown source.

Frequently asked questions

Why does Excel show strange characters like é in my CSV?
Older versions of Excel assume a legacy encoding unless the file starts with a UTF-8 byte-order mark. Keep Excel-friendly download ticked and accented letters and emoji will display correctly.

My CSV has a comma inside a value. Will it break?
Not if the value is in double quotes, which is how spreadsheet programs export it. The converter treats everything between the quotes as one value, including commas and line breaks.

What happens if rows have different numbers of columns?
Missing values are filled with an empty value (or null when type detection is on), and extra values get column names like column_5. The status line tells you how many rows were uneven so you can check the source.

Can I convert a JSON object that isn't an array?
Yes. A single object becomes one row. If the object has one property holding an array of records, such as {"data":[…]}, that array is used and the status line says so.

Is there a size limit?
No fixed limit. Files of several megabytes convert in a moment on a typical computer. The preview shows the first 20 rows; the output always contains everything.