CSV to JSON

What does this tool do?

It turns a CSV table into a JSON array of objects. The first row is read as the header, and each following row becomes an object. Everything runs locally in your browser.

How values are typed

Every cell is trimmed and then converted automatically:

There is no switch to turn this off, which matters for values that only look numeric:

• Leading zeros are lost. 01234 becomes 1234, so postal codes and zero-padded ids get corrupted.
• Long integers lose precision. Past 15–16 digits JavaScript numbers round: 12345678901234567890 becomes 12345678901234567000.
• 007.50 becomes 7.5.

If those values matter, make them non-numeric before converting (a text prefix such as zip:01234, for example) and strip it from the JSON afterwards.

Delimiters and quoting

• Only the comma separates fields. Semicolon- or tab-separated files are read as a single column, so convert them to commas first.
• Fields may be quoted with " and contain commas or line breaks. A doubled quote ("") is one literal quote.
• CRLF, CR and LF line endings are all accepted.
• A column with an empty header is skipped.
• If two headers share a name, the last column wins and the earlier one is dropped.
• Blank rows are ignored.

Converting back is not lossless

JSON to CSV and back is a one-way trip for types: a number becomes a number again, an empty field becomes "" rather than staying absent, and null comes back as an empty value. Keep the original file if you need an exact round trip.