CSV to JSON Converter

When should you convert CSV to JSON?

CSV is convenient for spreadsheet exports, while JSON is easier to use in APIs, configuration, frontend prototypes, and developer workflows.

This converter treats the first CSV row as field names. If duplicate headers are found, it warns you and keeps values with numbered keys instead of silently overwriting data.

How this converter reads CSV

CSV has no single formal standard the way JSON does; the closest widely cited reference is RFC 4180, which describes optional double-quoting of fields, escaping an embedded quote by doubling it, and comma as the default delimiter. Real-world exports vary: semicolons are common where a comma is already the decimal separator, and quoting conventions differ between spreadsheet applications. This tool runs a hand-written parser, not a wrapper around a CSV library, that follows the RFC 4180 quoting convention: a field can be wrapped in double quotes to contain the delimiter, a newline, or a literal quote character, and a literal quote inside a quoted field is written as two quote characters in a row.

The first non-blank row becomes the header row. Every following non-blank row becomes one JSON object, with header names as keys. Every value is kept as a JSON string; this converter does not infer booleans or numbers from cell text.

Worked examples

The Sample CSV button loads this data:

name,city,active,note
Alice,Bangkok,true,hello
Bob,Paris,false,cafe

Converting with a comma delimiter and 2-space indentation produces:

[
  { "name": "Alice", "city": "Bangkok", "active": "true", "note": "hello" },
  { "name": "Bob", "city": "Paris", "active": "false", "note": "cafe" }
]

Note that active stays the string "true", not the boolean true; every CSV value becomes a JSON string, since the parser has no way to know from plain text alone whether a column is meant to hold booleans, numbers, or text. A CSV with a repeated header, such as name,name, converts headers to name and name_2, with a warning listing name as duplicated, so the second column value is not silently dropped or merged into the first.

Limits and gotchas

• Every value becomes a string. Numbers, true and false, and blank cells all become JSON strings such as "42", "true", and "". Downstream code expecting real JSON numbers or booleans needs to convert them explicitly after import.
• Blank lines are dropped, not preserved. A fully empty line anywhere in the CSV, including between data rows, is skipped rather than becoming an empty JSON object or a gap in the array.
• Duplicate headers get an automatic suffix. Repeated header names become name, name_2, name_3, and so on, with a warning listing which base names were duplicated, so values are not overwritten silently.
• Blank header cells get a positional name. An empty header cell becomes field_1, field_2, and so on based on its column position, not its content.
• Unterminated quotes invalidate the whole file. If a quoted field never closes, the tool rejects the entire input and reports the row number where the parser lost track, rather than converting the rows that came before it.
• Only comma, semicolon, and tab delimiters are offered. Pipe-delimited or fixed-width text needs to be converted to one of those three delimiters before pasting it in.

Frequently Asked Questions

Is this CSV to JSON Converter free?

Yes. You can paste, convert, copy, and download JSON without signup.

Are CSV files uploaded?

No. CSV files are read and converted locally in your browser.

How are JSON keys created?

The first CSV row is used as the header row, and each following row becomes a JSON object.

What happens with duplicate headers?

The tool shows a warning and adds numbered keys so values are not silently overwritten.

Does it support Unicode?

Yes. UTF-8 text, accents, Asian scripts, and emojis are preserved in valid CSV fields.

Are numbers and true or false converted to real JSON types?

No. Every cell becomes a JSON string, including numeric-looking and boolean-looking values, since the parser has no reliable way to infer the intended type from plain text.

What happens to blank lines in my CSV?

Fully blank lines are skipped entirely and do not appear as empty objects in the JSON output.

Can I use a delimiter other than comma, semicolon, or tab?

Not directly. Only those three are offered; a pipe-delimited or fixed-width file needs to be converted to one of them before pasting it in.

Privacy

Privacy build: This build removes ads, analytics, remote fonts, runtime CDN scripts, and file-operation telemetry. Selected files are processed in the browser using local JavaScript and browser APIs.

ConvertUnlimited does not provide a server-side upload endpoint for this CSV to JSON conversion flow. Selected CSV files are processed locally in your browser.

Terms of Use

ConvertUnlimited is provided as is. Review generated JSON before using it in production systems.