JSON to CSV Converter - Flatten Nested JSON, Pick a Delimiter, Download

The tool checks your text with the browser's JSON parser and then reads the values itself, so that numbers and keys are kept exactly as you wrote them. If it is a list of objects, each object becomes one row. The columns are the union of the keys of every object, in the order they first appear, and a row that lacks a key gets an empty cell, so objects with different keys still line up. A single object becomes one row. A list of lists is written row by row, with shorter rows padded with empty cells, and a list of plain values gets one column called value. If the document is an object that holds the rows under one key, such as {"data": [...]}, the tool shows a button to use that list. Text with one JSON value on each line (JSON Lines) is read as a list too. Keys stay in the order they have in your document, even keys that are whole numbers such as "2".

Nested objects are flattened by joining the key names with a separator you choose, a dot by default, so {"address": {"city": "Kandy"}} gives a column called address.city. Switch flattening off to keep each nested object as JSON text in one cell. For lists inside a row you can join plain values into one cell (red; green; blue), spread them into numbered columns (tags.0, tags.1) or keep the list as JSON text. A list that holds objects cannot be joined, so it is kept as JSON text. A null becomes an empty cell. If two different keys flatten to the same column name, the later value wins and a warning says so.

Quoting follows RFC 4180. A field that contains the delimiter, a double quote, a carriage return or a line feed is wrapped in double quotes, and each quote inside it is doubled. You can quote every field instead. Rows end with CRLF, as RFC 4180 writes it, or with LF, and the file ends with a line break. The delimiter can be a comma, semicolon, tab or pipe. Excel on a computer whose regional settings use a comma as the decimal mark often expects semicolons, so if everything lands in one column, try the semicolon. Excel on Windows can read a UTF-8 file that has no byte order mark as a legacy encoding and show accented letters wrongly. The byte order mark option adds the three bytes EF BB BF to the downloaded file. The Unicode FAQ describes that mark as a signature that tells a program an unmarked file is UTF-8, and notes that some programs do not expect it, so the option is off by default. The mark is not added to the text you copy.

A spreadsheet can run a cell as a formula, and data from untrusted people can use that. OWASP calls it CSV injection and names cells that start with = + - @, a tab or a carriage return. The optional guard puts an apostrophe in front of any text cell that starts with one of those characters, so the spreadsheet shows it as text. It applies to text only: the JSON number -5 is left alone, but the string "-5" gets the apostrophe. It is off by default because it changes your data. The apostrophe stays visible in programs that do not hide it, and a phone number such as +94 77 123 4567 becomes '+94 77 123 4567. OWASP also warns that these protections are not reliable in Excel once the file has been saved and opened again, so treat the guard as one layer. Turn it on when other people will open the file and the values come from users.

Numbers are copied into the CSV exactly as they are written in your JSON, so 12345678901234567890 keeps every digit, 1.0 stays 1.0 and 1e400 stays 1e400. (The browser's own JSON.parse would turn them into 12345678901234567000, 1 and infinity.) Excel is the limit: Microsoft documents a number precision of 15 digits, so Excel keeps only 15 significant digits of a long ID when it opens the file. The tool counts whole numbers with more than 15 digits and warns you to import those columns as text. Lists of tens of thousands of rows convert in a moment. The result box shows the first 200,000 characters of a long result, and Copy and Download always use the whole result.