CSV to JSON Converter

What the converter does

The CSV to JSON Converter reads comma-separated text, with the first row as column names, and produces a JSON array with one object per data row. You paste the CSV or open a .csv or .tsv file, choose the delimiter, and press Convert to JSON. The output heading tells you how many rows were converted, and you can copy the result or download it as data.json. The conversion happens in your browser, so the data is not uploaded.

A worked example

The Try an example button loads a header row of name, age, zip and active, followed by Ada, 36, 02134, true and then "Sam, Jr.", 41, 90210, false. The result is an array of two objects.

• name: "Ada" and "Sam, Jr." are text. The comma in the second name is protected by quotation marks in the CSV.
• age: 36 and 41 become real numbers, because every value in the column is a number.
• zip: "02134" and "90210" stay as text. The first has a leading zero, so the column mixes text and numbers and nothing is converted. No digit is lost.
• active: true and false become real booleans.

How values get their type

The "Convert numbers, true/false and null" option works column by column. A column is converted only when every non-empty value in it has the same type. If it is all numbers, they become numbers. If it is all true and false, they become booleans. If any value is different, such as a ZIP code with a leading zero, the whole column stays as text, so a column never ends up holding a mix of strings and numbers. Empty cells become empty strings, not null. Numbers with 16 or more characters stay as text to avoid rounding. Untick the option and every value is kept exactly as written.

Headers, delimiters and quoting

The first row becomes the keys of every object. A blank header cell is named column1, column2 and so on by position. If two columns share a name, the later one overwrites the earlier one, so rename duplicates before converting. The delimiter can be a comma, semicolon, tab or pipe, which covers most exports from spreadsheets and databases. Quoted fields may contain delimiters, doubled quotation marks and even line breaks, and a byte-order mark at the start of a file is removed. A row with fewer cells than headers gets empty strings, and cells beyond the last header are ignored.

Errors you may see

The tool needs a header row and at least one data row, and it says so when there is only one line. If a quoted field never closes, it reports that, which usually means a stray quotation mark. After conversion, the output goes straight into the JSON Formatter if you want a different indent or compact output, or into the JSON Validator if you want to double-check it.

What it does not do

Flat CSV produces flat JSON. A column called address.city becomes a key named "address.city" and is not rebuilt into a nested object. Dates stay as text, because JSON has no date type. If your target system expects a particular structure, reshape the output afterwards. To go back to a spreadsheet, use the JSON to CSV Converter, and if the JSON you produce is rejected by an API, the guide to common JSON errors explains the usual causes.