How to use
- 1Choose CSV → JSON or JSON → CSV.
- 2Paste your data; the delimiter is detected automatically or can be set to comma, semicolon, tab or pipe.
- 3Set the options: header row, type inference, flattening of nested objects, BOM for Excel.
- 4Copy the result, download it as data.json or data.csv, or swap it back into the input.
CSV parsing done properly
The parser follows the RFC 4180 conventions: fields that contain the delimiter, line breaks or quotes are wrapped in double quotes, and a quote inside a field is written as two quotes ("") — so "Smith, John" stays one field. Auto-detection checks the first ten lines for commas, semicolons, tabs and pipes and picks the delimiter that splits every line into the same number of columns. With “First row is header” on, each row becomes a JSON object keyed by the column names (empty headers become column1, column2…, duplicate names get a suffix); with it off, you get an array of arrays.
Type inference
CSV has no data types, so without inference every value is a string. With “Infer types” on, numbers become JSON numbers, true/false become booleans and null becomes null, while empty cells stay empty strings. Values that would be damaged as numbers are kept as strings: integers longer than JavaScript can store exactly (above 9,007,199,254,740,991), such as long IDs, and values with leading zeros, such as the ZIP code 02134.
JSON to CSV and Excel
For JSON → CSV, paste an array of objects (a single object works too). The columns are the union of all keys, so records with missing fields simply get empty cells. Nested objects can be flattened into dot-notation columns such as address.city, and arrays are written as JSON text in a single cell. Excel only opens UTF-8 CSV files with accented characters correctly when the file starts with a byte-order mark, so tick “UTF-8 BOM for Excel” before downloading for Excel. Semicolon-separated exports from European Excel versions are detected automatically.
Frequently asked questions
How do I convert a CSV file to JSON?
Open the file in a text editor, copy its contents and paste them here with CSV → JSON selected. The JSON appears instantly and can be downloaded as data.json.
Why are some numbers in quotes in the JSON?
Either type inference is off, or the value has a leading zero or too many digits to be stored safely as a number. Turn on “Infer types” to convert numeric columns.
Does it handle commas inside values?
Yes, as long as the value is enclosed in double quotes, as standard CSV requires.
Is my data uploaded?
No. Conversion happens in your browser, so you can safely convert customer lists and database exports.
Not happy with the results?
Talk to Webin Agency about fast, SEO-friendly websites, e-commerce and Google Ads management.