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Document Format

CSV

Comma-Separated Values

CSV (Comma-Separated Values) is the simplest and most universal format for exchanging tabular data. No software can't read it, no database can't import it, and no programming language lacks CSV support. CSV is the lowest common denominator of data — which is both its greatest strength and its biggest weakness.

What is CSV?

A CSV file is a plain text file where each line represents one row of data and values are separated by commas (or sometimes tabs, semicolons, or pipes). The first line is often a header row with column names. Every spreadsheet application, database, and data analysis tool reads CSV. A CSV file with three rows and three columns looks like: name,age,city Alice,30,New York Bob,25,London. That's it. No formulas, no formatting, no data types — just text. The simplicity is the point. CSV was standardized in RFC 4180 (2005), though implementations vary: some use semicolons as delimiters (common in European locales where commas appear in numbers), others use tab characters. Values containing commas or line breaks must be wrapped in double quotes. A value with a quote character must escape it as two consecutive quotes. Despite this simplicity, CSV edge cases trip up many parsers — incorrectly handling quoted fields, line endings (CRLF vs LF), encoding (UTF-8 vs ASCII vs Latin-1), and BOM (Byte Order Mark) headers. File size: CSV is uncompressed text, so a CSV with 100,000 rows and 20 columns of typical data might be 5-20MB. The equivalent XLSX is often smaller due to ZIP compression.

CSV pros and cons

Advantages

  • Universal compatibility — every tool that handles data reads CSV
  • Human-readable in any text editor
  • No proprietary format — open and documented standard
  • Fastest format to parse programmatically
  • Works in all programming languages without special libraries
  • Perfect for data interchange between different systems

Limitations

  • No data types — everything is text (dates, numbers, booleans need interpretation)
  • No support for multiple sheets or hierarchical data
  • No formulas, formatting, or charts
  • Encoding issues (UTF-8 vs Latin-1) cause character corruption
  • No schema — column meaning depends on documentation
  • No standard for special values like null, NaN, or infinity

When should you convert CSV files?

Convert CSV to XLSX when you need formulas, formatting, multiple sheets, or charts — when the data needs to be presented, not just stored. Convert CSV to JSON when working with web APIs or applications that need hierarchical data structures. Convert XLSX or database exports to CSV when you need to share data with any system — CSV is always the safe choice for interoperability. Convert CSV to Parquet or Arrow for large-scale data processing (CSV is slow to parse at millions of rows).

Convert CSV files

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CSV FAQ

Why does my CSV look wrong when opened in Excel?
Excel mishandles CSV in two common ways: (1) Delimiter — Excel may use semicolons instead of commas based on your system locale. Fix: change the delimiter in the CSV, or use Excel's Text Import Wizard (Data → From Text/CSV). (2) Encoding — Excel sometimes interprets CSV as Windows-1252 encoding instead of UTF-8, corrupting non-ASCII characters (accented letters, emojis, Chinese characters). Fix: save the CSV with a BOM (Byte Order Mark) at the start, which signals UTF-8 to Excel. In Python: with open('file.csv', 'w', encoding='utf-8-sig').
What's the maximum size of a CSV file?
CSV itself has no size limit. The practical limit is what your software can handle: Excel has a 1,048,576 row limit per sheet. Google Sheets has a 10 million cell limit. Most programming languages (Python, R) can read arbitrarily large CSV files with streaming parsers. For very large CSV files (100MB+), consider converting to Parquet (columnar format, much faster to query) or loading into a database.
Is TSV better than CSV?
TSV (Tab-Separated Values) solves CSV's comma confusion — if your data contains commas in values (like addresses or names), TSV avoids the quoting complexity. But TSV files are less universally recognized by import wizards. Most tools accept both. The practical choice: use CSV if your data doesn't contain commas in values; use TSV if it does and you want to avoid quoted fields.

More formats

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