Convert a table between CSV and JSON
Convert CSV to JSON using column headers as object keys, or convert a JSON array of flat objects or rows back to CSV. CSV values remain strings, preserving identifiers and leading zeros instead of guessing which fields should become numbers, dates, or booleans.
CSV and JSON conversion examples
Keep a postal code as text
Input
name,zip Ada,00123
Result
[
{
"name": "Ada",
"zip": "00123"
}
]Leave CSV has a header row enabled. Both fields become JSON strings, including the postal code with its leading zeros. If a downstream system needs numeric types, map those fields explicitly after reviewing their meaning.
Detect a semicolon-separated file
Input
name;score "Smith, John";42
Result
[
{
"name": "Smith, John",
"score": "42"
}
]Auto-detect recognizes the semicolon as the field separator while preserving the comma inside the quoted name. The status message names the selected separator so you can verify the interpretation before using the generated JSON.
Turn flat JSON objects into CSV
Input
[{"name":"Ada","zip":"00123"},{"name":"Sam","zip":"90210"}]Result
name,zip Ada,00123 Sam,90210
Choose JSON → CSV and keep object keys as a header row. A spreadsheet may infer numbers when opening the resulting CSV, so import postal codes as text there too; CSV itself does not store column types.
How to convert your table
- Paste CSV or JSON, open a file, or drop it into the input area. Choose the direction that matches your source format.
- For CSV, check whether the first row contains headers. Start with Auto-detect, or choose the known separator manually.
- Review the output and any separator or validation message. Resolve ambiguous separators, duplicate headers, or nested values rather than guessing at a mapping.
- Copy the result or download it as a file. Check a few representative records, including identifiers and empty fields, before importing it into another system.
CSV to JSON questions
Why did my CSV become one column?
A single-column file is valid, but an unexpected single column can mean the separator was not recognized. Choose comma, semicolon, tab, or pipe explicitly. Auto-detect samples the beginning of the input and asks you to choose when more than one separator fits.
Can I convert nested JSON or missing fields?
Nested objects and nested arrays need flattening before conversion. Flat object rows can have different keys: CSV uses their combined columns, with missing fields and null values becoming empty cells. Duplicate JSON property names are rejected rather than silently overwritten.
Are JSON numbers rounded during CSV conversion?
No. Number tokens retain their exact written values, including long integers and exponent notation. CSV-to-JSON deliberately keeps all cell values as strings. These choices protect source values, but converting in both directions is not a lossless type-preserving round trip.
Is conversion private, and how large can files be?
The file contents stay in your browser; no conversion upload, ads, or Data Pass is required. Input is limited to 10 MiB and tables to 250,000 cells. Large results and slow operations are stopped; use smaller tables when a limit is reached.
A table converter, not a format mapper
This tool does not flatten nested JSON, infer column types, or convert XML. CSV also cannot retain the distinction between null, missing, and empty text.