File extension

.csv

Comma Separated Value Files

.csv files are comma-separated values: a plain-text tabular format with one record per line and fields separated by commas, used as a simple, near-universal interchange format for spreadsheets and databases.

Known meanings

Formats and reference material for .csv

Comma Separated Value Files

Comma Separated Value Files

  • spreadsheets
  • Robert J. Lynch and Paul Hsieh
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Details

Format notes

Comma-Separated Values (CSV)

CSV is the most common plain-text format for exchanging tabular data. Each line is one record, and fields within a record are separated by commas, with an optional header row naming the columns. Its appeal is universality and simplicity: almost every spreadsheet, database, and analysis tool can import and export CSV, and the files are human-readable and easy to generate.

The format’s conventions are documented in RFC 4180. Fields that contain a comma, a double quote, or a line break are enclosed in double quotes, and a literal double quote inside a quoted field is written as two double quotes. This quoting is what allows arbitrary text to be carried safely in a comma-delimited line.

Ambiguities

CSV is deceptively simple and not fully standardized in practice. Real files vary in delimiter (comma, semicolon, or tab — the latter often called TSV), character encoding (which affects non-ASCII text and is a frequent source of corruption), line-ending style, and whether a header row is present. Some locales use the semicolon because the comma is a decimal separator. Reliable interchange therefore means stating the encoding and delimiter explicitly rather than assuming them.

Preservation And Security Notes

CSV is excellent for preservation of tabular data because it is open, text-based, and tool-independent; recording the encoding (ideally UTF-8) and delimiter keeps it self-describing. A well-known risk is CSV (formula) injection: a value beginning with =, +, -, or @ may be interpreted as a formula when the file is opened in a spreadsheet, so values should be sanitized on export from untrusted input.

Further Reading

  • RFC 4180 (Common Format for CSV Files): https://datatracker.ietf.org/doc/html/rfc4180