JSON to CSV

Paste JSON on the left. The columns are the keys, in the order they first appear, and every object becomes a row. Swap the boxes to read a CSV back into JSON.

Nested values decides what happens to an object inside an object. A column per leaf gives you user.name and user.id, flattened with dots. Keep as JSON in one cell leaves the structure intact inside a single field, which is what you want if the file is going somewhere that will parse it again.

Separator covers the two things people call CSV that use a semicolon or a tab instead. Reading CSV sets whether 12 comes back as a number or as text.

A field holding a comma has to be quoted, or the row grows a column. Quotes inside a field are doubled. A newline needs quoting too, and then the file has a record spanning two lines, which breaks anything that reads it line by line.

This converter does all three, in both directions. The reader is a character-by-character pass rather than a split on commas, because a split on commas is wrong the moment any field contains one.

What it can't fix is ragged data. A short row is padded with empty strings rather than shifted, and a row longer than the header loses the extra fields, because there is nothing to call them.

CSV ran for decades with no specification at all. RFC 4180 arrived in October 2005 and is careful about what it claims: it is an Informational RFC that documents "the format that seems to be followed by most implementations" rather than defining it.

So files disagree. The RFC says records end with CRLF, and plenty of files end their lines with a bare newline instead. It says fields may be quoted, and some writers quote everything. Excel picks its separator from your locale, so a French machine writes semicolons and a CSV mailed across a border stops parsing.

Don't trust a CSV's separator until you've looked at its first line. Separator has a Semicolon option for that French file.

JSON to YAML keeps the nesting that CSV has to flatten away, and it's the better fit for configuration files. JSON to XML does the same for anything that has to go into an older system.

If your JSON is going into a string in source code rather than into a file, JSON escape is the one you want.