CSV to JSON Converter

Updated October 18, 2026Free mock REST & WebSocket APIs

Paste CSV or drop a .csv/.tsv file to get JSON instantly. The delimiter is detected for you, quoted fields with commas and line breaks are parsed correctly, and numbers and booleans come out as real JSON types.

CSV

Paste, type, or drop a file onto the box.

Delimiter

Output

First row is the headerDetect numbers, booleans and nullNest “a.b” columns into objectsMinify JSON

id	name	email	address.city	address.zip	active
1	Ada Lovelace	ada@example.com	London	W1	true
2	Grace Hopper	grace@example.com	New York	10001	false
3	José "Pepe" Núñez	jose@example.com	Sevilla, ES	41001	true

3 rows × 6 columns

JSON

[
  {
    "id": 1,
    "name": "Ada Lovelace",
    "email": "ada@example.com",
    "address": {
      "city": "London",
      "zip": "W1"
    },
    "active": true
  },
  {
    "id": 2,
    "name": "Grace Hopper",
    "email": "grace@example.com",
    "address": {
      "city": "New York",
      "zip": 10001
    },
    "active": false
  },
  {
    "id": 3,
    "name": "José \"Pepe\" Núñez",
    "email": "jose@example.com",
    "address": {
      "city": "Sevilla, ES",
      "zip": 41001
    },
    "active": true
  }
]

🔒 Runs in your browser — nothing you paste is uploaded.

How to convert CSV to JSON

Paste the CSV, drop a file onto the box or click Open file. The delimiter is auto-detected (or pick one).
Choose whether the first row is a header, and whether you want an array of objects or an array of arrays.
Check the preview table and any warnings, then copy the JSON or download it as a .json file.

What the converter does with your values

CSV cell	JSON (typed)	Why
`42`, `-3.5`	`42`, `-3.5`	Plain numbers become numbers
`true` / `FALSE`	`true` / `false`	Booleans
(empty)	`null`	Missing value
`007`, `01234`	`"007"`	Leading zeros are codes (ZIPs, IDs), not numbers
`12345678901234567890`	string	Too big for a JavaScript number without losing digits
`1,5`	`"1,5"`	Decimal commas are left as text

Turn off “Detect numbers, booleans and null” to keep every value as a string, exactly as written.

Nested JSON from flat columns

Headers with dots are rebuilt into objects, and numeric segments into arrays — the reverse of what our JSON to CSV converter does:

id,user.name,user.email,tags.0,tags.1
1,Ada,ada@example.com,math,poet

→ [{ "id": 1, "user": { "name": "Ada", "email": "ada@example.com" }, "tags": ["math", "poet"] }]

How delimiter detection works

The converter counts commas, semicolons, tabs and pipes outside quotes on the first 20 lines and picks the one that appears the same number of times on every line. That's why 1,5;2,5 (European decimals with semicolons) is correctly read as two columns.

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Frequently asked questions

Is my CSV uploaded anywhere?

No. The conversion runs entirely in your browser with JavaScript, so your CSV never leaves your device and isn't logged or stored.

Does it handle commas and line breaks inside quoted fields?

Yes. It follows RFC 4180: quoted fields may contain the delimiter, line breaks and doubled quotes (""), and CRLF, LF or CR line endings all work.

What if my CSV has no header row?

Untick “First row is the header”. Columns are then named column1, column2…, or choose “Array of arrays” to get plain rows.

What happens with duplicate column names?

They're renamed with a suffix (email, email_2) so no data is lost, and a warning tells you.

Can it read TSV or pipe-delimited files?

Yes — tab, pipe, semicolon and comma are all detected automatically.

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