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Sealpaste

CSV to JSON Converter

Turn a CSV or spreadsheet export into a JSON array of objects, using the first row as keys.

Direction
Delimiter

Input CSV

JSON

How to use it

  1. 1Paste CSV (first row = column names) or open a .csv file.
  2. 2Leave the delimiter on Auto, or pick comma, semicolon or tab.
  3. 3Choose whether numbers and true/false become typed values, then copy or download the JSON.

Private by design

Everything runs in this browser tab. Your input is never uploaded, logged or saved on a server, and there are no public "recent" pages. Close the tab and it's gone.

How we keep it private

Examples

Typed values and nesting

Leading zeros are kept as text, so zip codes and IDs are not damaged.

Input

id,user.name,zip,active
1,Ada,02134,true

Output

[
  {
    "id": 1,
    "user": {
      "name": "Ada"
    },
    "zip": "02134",
    "active": true
  }
]

Type detection rules

With "Detect numbers and booleans" on:

  • Plain decimal numbers like 42 or -3.5 become JSON numbers.
  • Numbers with leading zeros (02134) and integers too large for JavaScript stay strings.
  • true and false become booleans; an empty cell becomes null.
  • Everything else stays a string. Turn detection off to keep every value as text.

Frequently asked questions

Does it handle quoted fields with commas and line breaks?

Yes. Standard CSV quoting is supported: "Hopper, Grace" stays one value, and doubled quotes inside a field are unescaped.

Can I get nested JSON from a flat CSV?

Yes. Keep "Nest dotted columns" on and a column named address.city becomes {"address": {"city": …}}.

Is my data uploaded?

No. The conversion runs in your browser, so exports with customer or user data never leave your computer.