CSV to JSON converter

RFC 4180 is the closest thing CSV has to a specification, and the three rules that matter are all about quotes. A field may be wrapped in double quotes. A quoted field may contain the delimiter, a carriage return or a line feed. A quote inside a quoted field is written twice.

That is why splitting a CSV on commas is wrong so often. The sample loaded above contains a note with a comma in it, a note with a line break in the middle, and a note containing doubled quotes. A naive split produces four broken rows from those three records. The parser here walks the text one character at a time and tracks whether it is inside quotes, so all three survive the trip.

Going the other way is lossy in a different direction, because JSON has nesting and CSV does not. Two decisions are worth knowing about.

The header is the union of every key. If the first record has no middle name and the second one does, the column still appears and the first record gets an empty cell, rather than every later value shifting one column left.

Nested values are written as JSON text in the cell. An address object becomes readable JSON inside one column instead of being dropped or exploded into columns that would not survive a round trip.

Typed output looks tidier, right up until a ZIP code of 02138 becomes 2138, a student ID of 0004 becomes 4, and a phone number in scientific notation becomes unusable. CSV has no types, so any conversion is a guess about intent.

The safe default is to keep every value a string and let you opt in. Turn on number and boolean detection when the data is genuinely numeric, such as scores, prices or counts.

Does this handle commas inside quoted fields?

Yes. The parser follows RFC 4180, so a field wrapped in double quotes can contain commas, line breaks and doubled quotes without breaking the row. The preview table shows exactly how each row was split.

Can it convert JSON back to CSV?

Yes, in both directions. Give it an array of objects and it builds the header from the union of all keys, so a record missing a field still lines up under the right column instead of shifting the row.

What happens to nested objects and arrays in my JSON?

A nested value is written into the cell as JSON text rather than being dropped or flattened into extra columns. CSV has no nesting, so this keeps the data readable and reversible.

Why are my numbers coming out as strings?

By default every CSV value stays a string, because typing them would strip the leading zeros from ZIP codes, student IDs and phone numbers. Turn on number and boolean detection if you want typed values instead.

Does it support semicolon or tab separated files?

Yes. The delimiter is detected from your file, counting only separators outside quoted fields, and you can override it if the guess is wrong.

Is my data uploaded to a server?

No. Parsing runs in your browser, so spreadsheets with customer or student data never leave your device.