How to Convert CSV Data Into JSON
A CSV is a grid: a header row naming the columns, then one row per record. JSON is nested objects. Converting means turning each row into an object whose keys come from the header. The CSV to JSON Converter does it in your browser.
How the mapping works
The first row is special. Its cells become the keys of every object, so a header of name, email, age produces objects with those three keys, one object per data row, collected into an array.
That is the whole transformation, and it explains the limits. CSV is flat, so the output is an array of flat objects - there is no way for a CSV to express a nested structure or a list inside a field without a convention you invent yourself.
Quotes, commas and the bits that go wrong
A comma inside a value is the classic problem, and the solution is quoting: a field containing a comma is wrapped in double quotes, and a double quote inside such a field is written twice. A proper parser handles both; splitting on commas yourself does not, which is why hand-rolled CSV parsing breaks on the first address field.
Every value comes out as a string, because CSV has no types. The age column gives you "42", not 42. If your consumer expects numbers it has to convert them, and that is where empty cells bite - an empty field is an empty string, which is not zero and not null, and deciding which it should become is a judgement the converter cannot make for you.
Then the small ones. A leading zero in a reference number survives in CSV and is often destroyed by a spreadsheet before you ever export. Line breaks inside a quoted field are legal and surprise most naive parsers. And a file saved from a spreadsheet in a non-English locale may use semicolons as separators, because the comma is the decimal mark there.
Check before you convert
Open the file and look at the header row: duplicated column names produce objects where one key overwrites the other, and a blank column name produces a key you cannot address. Both are worth fixing in the CSV rather than in the JSON.
Afterwards, format the result with the JSON Formatter and read the first object. If the keys are right and the values are the right shape, the other ten thousand rows almost certainly are too.
Common questions
Can I get nested JSON out of a CSV?
Not directly. Flat objects are what a flat file can express. Nesting needs a post-processing step with rules you define.
What about going the other way?
The JSON to CSV Converter flattens an array of objects back into rows.
Why are my numbers quoted?
Because CSV stores everything as text and the converter does not guess types. Convert them where you consume them.
Is my file uploaded?
No. The conversion runs in your browser, which matters for a customer export.
Got a spreadsheet export to convert?