CSV (Comma-Separated Values) is a plain-text file format for tabular data. Each line represents a row; fields within a row are separated by commas (or another delimiter like a tab or semicolon). The first row is typically a header row with column names.

How are commas inside CSV fields handled?

If a field contains a comma, newline, or double-quote, it must be wrapped in double quotes. Any double-quote within such a field is escaped by doubling it: a field containing He said "hello" is written as "He said ""hello""".

What is the difference between CSV and TSV?

TSV (Tab-Separated Values) uses a tab character as the delimiter instead of a comma. TSV avoids the quoting complexity of CSV for data that frequently contains commas (e.g. addresses), but tab characters in data still require escaping.

What is CSV?

CSV (Comma-Separated Values) is a plain-text format for tabular data. Each line is a row; fields are separated by commas. It is the most universally supported data exchange format — readable by Excel, Google Sheets, databases, and virtually every programming language.

Structure

A typical CSV file looks like:

name,age,city
Alice,30,London
Bob,25,Paris

The first row is conventionally a header row. Fields containing commas or newlines must be quoted with double quotes. A double-quote inside a quoted field is escaped by doubling it: "".

Common Delimiters

Comma (,) — standard CSV, used in English-locale exports
Semicolon (;) — common in European locales where comma is the decimal separator
Tab (\t) — TSV (Tab-Separated Values), avoids comma quoting issues
Pipe (|) — sometimes used in data pipelines to avoid delimiter conflicts

Common Gotchas

Encoding — Excel often saves as Windows-1252 rather than UTF-8; non-ASCII characters may corrupt on import
Line endings — Windows CRLF (\r\n) vs Unix LF (\n) can confuse some parsers
Leading zeros — Excel auto-formats numbers, stripping leading zeros from ZIP codes, phone numbers, etc.
No schema — CSV has no type information; parsers must infer or be told whether a column is a string, number, or date

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Frequently Asked Questions

Does CSV support nested data?

No. CSV is flat — it cannot represent nested objects or arrays. For nested data, use JSON or XML. A common workaround is to store a JSON string inside a CSV field, but this is fragile and hard to query.

What RFC defines CSV?

RFC 4180 defines a common format for CSV, but it is not enforced — many programs produce subtly incompatible CSV. Always test imports from third-party sources.

Related Terms

JSON — The structured alternative to CSV for nested data.
XML — Another structured format often compared to CSV.