CSV file format: what it is and how to use it

CSV is the lingua franca of tables: rows and columns as plain text that every spreadsheet, database and script can read. Learn when to use it and what to choose instead.

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What is a CSV file?

A .csv file is a table stored as comma-separated values: one row per line, fields divided by commas, fields containing commas or quotes wrapped in double quotes. Formalized late in RFC 4180, it is decades older in practice. It carries no types, no styles, no multiple sheets: just the grid, which is precisely why every spreadsheet, database, BI tool and programming language can read it.

When should you use CSV?

  • Data exchange between systems: exports and imports that must work everywhere.
  • Version-controlled data: diffs on plain text actually mean something.
  • Script ingestion: pandas, Excel, SQL loaders all eat it natively.

When is another format a better fit?

For real spreadsheet work (formulas, styles, multiple sheets) use XLSX or ODS. For nested or typed data use JSON; for documents, obviously not CSV. And beware its famous traps: encoding (use UTF-8), the delimiter that is not always a comma, and Excel happily mangling IDs and dates on open.

The short version: CSV is the lowest common denominator of data, unbeatable for exchange and deliberately empty of everything else.

How to open a CSV file

On Windows

Double-click the file, or open it with Microsoft Excel.

On macOS

LibreOffice Calc opens CSV files on macOS.

In your browser

Open CSV files right in a browser tab or with the dexrr viewer. No install, no upload.

Also opens in

  • Microsoft Excel
  • LibreOffice Calc
  • Google Sheets
  • Any text editor

View or convert CSV files

A quick preview or a new format. No install, no upload.

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CSV technical details

Full name
Comma-Separated Values
Extensions
.csv
MIME type
text/csv
Compression
None (uncompressed)
Specification
datatracker.ietf.org

CSV questions, answered

How do I open a .csv file?

Excel, Google Sheets, LibreOffice Calc, pandas, anything tabular opens it; a text editor shows the raw form. dexrr displays and converts csv files in your browser.

Can I convert CSV files online?

Yes, dexrr converts csv locally in your browser: CSV to XLSX for spreadsheet work, CSV to JSON for applications or CSV to PDF for printing.

Why does Excel break my CSV data?

Excel guesses types on open: 00123 becomes 123, 2024-01 becomes a date, long IDs become scientific notation. Import via Data → From Text/CSV and set column types explicitly.

What is the difference between CSV and XLSX?

CSV is the raw grid as text, with no types, styles or multiple sheets. XLSX is a full workbook. CSV wins for exchange between systems, XLSX for working in.

Is the CSV format outdated?

Despite its quirks it is more used than ever. It is the one table format every tool on the planet can read and write.