Guide
About CSV and JSON Conversion
CSV to JSON
With First row is header on, each row becomes an object whose keys are the column names, which is the format most APIs and JavaScript code expect. With it off, each row becomes an array. Detect numbers and booleans turns 42 into a number and true into a boolean instead of keeping them as text.
The parser follows RFC 4180: fields containing commas, quotes or line breaks can be wrapped in double quotes, and a literal quote inside a quoted field is written twice ("").
JSON to CSV
Paste an array of objects. Every key found in any object becomes a column, so rows with missing fields still line up. Nested objects are flattened into dot-notation columns such as address.city, and arrays are written as JSON text in a single cell.
Opening CSV files in Excel
- In countries that use a comma as the decimal separator, Excel expects semicolons. Choose the Semicolon delimiter when exporting for those users.
- Excel may drop leading zeros (ZIP codes, phone numbers) and turn long IDs into scientific notation. Import the file with Data > From Text/CSV and set those columns to Text.
Frequently asked questions
Is there a file size limit?
No fixed limit; files are processed in your browser's memory. Tens of thousands of rows convert in about a second on a typical laptop. Only the first 50 rows are shown in the table preview.
Why are some values strings instead of numbers?
Turn on 'Detect numbers and booleans'. If you need to keep values like ZIP codes or IDs with leading zeros exactly as written, leave it off.
Is my data sent anywhere?
No. Parsing and conversion run entirely in your browser, so it is safe to use with customer or financial data.