CSV to JSON Converter — Free Online Tool
Convert CSV data to JSON format online. Supports headers, custom delimiters and file upload. Free, browser-based.
CSV (Comma-Separated Values) is a universal data exchange format, but JSON is the native format of web APIs and JavaScript applications. This tool converts CSV data to a JSON array of objects, using the first row of the CSV as the object keys. It uses the robust PapaParse library which handles edge cases including quoted fields containing commas, multi-line values, and different line endings. You can either paste CSV text directly or upload a .csv file.
How to use
- Paste your CSV data into the input area, or upload a .csv file using the file button.
- Click 'Convert to JSON' to convert the CSV to a JSON array.
- Copy the JSON to clipboard or download it as a .json file.
FAQ
How does the converter handle the CSV header row?
The first row of the CSV is treated as the header row and becomes the keys of each JSON object. For example, a CSV with columns 'Name,Age,City' produces JSON objects like {"Name": "Alice", "Age": "30", "City": "London"}. All values in the JSON are strings unless you post-process them. If your CSV has no header row, the output will use the first data row as keys, which is usually undesirable — add a header row first.
What delimiters are supported besides comma?
PapaParse automatically detects the delimiter in your CSV. If your file uses tabs (TSV), semicolons (common in European locales where commas are used as decimal separators), pipes, or other characters, the library will detect and use the correct delimiter. You do not need to configure this manually.
How are quoted fields and fields containing commas handled?
RFC 4180 CSV quoting is fully supported. Fields that contain commas, double quotes, or newlines should be enclosed in double quotes in the CSV source. An embedded double quote is escaped by doubling it (""). PapaParse correctly parses all of these cases. For example, "Smith, John","30" is correctly parsed as two fields: 'Smith, John' and '30'.
What is the maximum file size for CSV upload?
There is no hard limit imposed by this tool. The conversion is handled entirely in the browser. Practical performance depends on your device — CSV files up to 10MB convert in well under a second on modern hardware. Very large files (100MB+) may cause the browser tab to become temporarily unresponsive during parsing.
Are all values in the JSON output strings?
Yes, by default all values are output as JSON strings, even numbers and booleans, because CSV has no type system. If you need typed values (numbers as numbers, true/false as booleans), you will need to post-process the JSON or use a tool that performs type inference. This conservative approach avoids data loss — for example, a leading zero in a zip code ('01234') would be lost if parsed as a number.
Is the conversion done in my browser or on a server?
The conversion runs entirely in your browser using the PapaParse library. Your data is never uploaded to any server. This is important for CSV files that may contain personally identifiable information (PII), financial data, or other sensitive content.