CSV ↔ JSON Converter

Why splitting on commas is not parsing CSV

The most common CSV bug in the world is line.split(","). It works on your sample data and silently corrupts real data the moment a value contains a comma, a quote, or a newline. CSV is not "values separated by commas" — it is a small grammar with quoting rules, codified loosely in RFC 4180 (2005). Consider this single, perfectly valid row:

id,name,note
7,"Doe, Jane","Said ""hello"" and
then left"

A naive split produces five garbage columns. A correct parser produces exactly three fields: 7, Doe, Jane, and a note whose value is Said "hello" and followed by a real line break and then left. This tool produces the second result. Here is the JSON it returns:

[
  {
    "id": 7,
    "name": "Doe, Jane",
    "note": "Said \"hello\" and\nthen left"
  }
]

CSV pitfall reference: what breaks and how this tool handles it

These are the edge cases that quietly break spreadsheets, ETL jobs, and import scripts. The middle column is what a naive comma-splitter does; the right column is this converter's actual behavior (it uses an RFC 4180-aware parser with header detection and type inference).

The leading-zeros row is the one place automatic typing can bite you. If your CSV has ZIP codes, phone numbers, or fixed-width IDs, wrap them in quotes and prefix with a non-numeric marker, or convert them after import — see the FAQ.

Comma, semicolon, or tab? Detecting the real delimiter

"CSV" is a misnomer half the time. The actual separator depends on where the file came from, and the most common surprise is regional. In locales that use a comma as the decimal mark (most of continental Europe), Excel exports use a semicolon so that 1,5 stays one number. Files copied straight out of a spreadsheet cell range are usually tab-separated. Here is how to recognize each:

If your converted JSON comes back as a single key holding the entire row, you have the wrong delimiter selected. Switch the Delimiter dropdown above the editor and the output updates instantly.

Going the other way: what happens to nested JSON

CSV is flat; JSON is not. When you convert JSON → CSV, every object should be a flat key/value record. The tool reads an array of objects (a bare object is wrapped in a one-element array for you), takes the column headers from the keys of the first object, and quotes any value that contains the delimiter, a quote, or a newline — round-tripping cleanly back to JSON. For predictable columns, make sure the first record contains every key your data uses.

Nested structures have no native CSV representation, so plan for them:

• Nested values do not survive cleanly. A nested array is flattened into the cell (e.g. tags: ["a","b"] is written as a,b in one quoted column), and a nested object is coerced to [object Object] — neither round-trips back to its original structure. Stringify nested fields yourself before converting if you need to recover them.
• Mismatched keys: the header row is taken from the first object only. If a later record is missing one of those keys, its cell is left empty; if a later record has an extra key that the first record lacks, that value is dropped. Keep your records uniform — or put a record with the full key set first.
• If you need true flattening (address.city as its own column), flatten the JSON first; CSV has no concept of nesting.

CSV-to-JSON questions developers actually ask