What is a CSV file?
CSV is plain text where each line is a row and values are separated by commas. It is the most portable tabular format in existence and has no types, no formulas and no sheets. Its weakness is ambiguity: quoting, encodings and delimiters vary between tools.
At a glance
- Full name
- Comma-Separated Values
- Extensions
- .csv
- Type
- Data
- Introduced
- 1972 (RFC 4180 in 2005)
- Created by
- Long-standing convention, later documented as RFC 4180
- Compression
- None
- MIME type
- text/csv
Strengths
- Readable by essentially every spreadsheet, database and language
- Plain text, so it diffs and streams well
- No practical size limit
Limitations
- No data types, so leading zeros and long numbers get mangled
- No multi-sheet support, formulas or formatting
- Delimiter, quoting and encoding conventions differ between tools
When to use CSV
Moving tabular data between systems, or handling files too large for a spreadsheet.
You need formulas, formatting, multiple sheets or guaranteed types. Use XLSX.
Convert CSV files
Every tool below runs in your browser unless it is labelled otherwise, so the file stays on your device.
JSON ⇄ CSV
Converts JSON arrays into CSV spreadsheets, or CSV files back into JSON, correctly handling quoted, escaped, and nested values.
CSV ⇄ Excel
Converts CSV files into full Excel spreadsheets, or existing Excel workbooks back into plain, portable CSV text data files.
CSV Cleaner & Deduper
Cleans, deduplicates, transforms, and validates CSV data in bulk before exporting a corrected, ready-to-use output file.
CSV Diff
Compares two CSV files row by row and clearly highlights exactly which rows were added, removed, or changed between them.
CSV conversions
Each page states what the target format cannot carry before you run it.
CSV compared
Related data formats
Last updated 2026-08-03