Files and data
What is CSV?
Short for Comma-separated values.
CSV is a plain-text format that stores table rows as lines and separates the fields in each row with a delimiter, usually a comma.
How it works
CSV is the lowest common denominator for tables. Every spreadsheet, database and programming language can read and write it, which makes it the usual way to move simple tabular data between systems.
Each line is one row. Within a line, a delimiter separates the fields. Fields containing that delimiter, quotes or line breaks are wrapped in double quotes, and a quote inside a quoted field is doubled. Some regions and exports use semicolons or tabs instead of commas, so the delimiter matters when importing.
CSV vs XLSX
| Feature | CSV | XLSX |
|---|---|---|
| Stored as | Plain text | Zipped XML workbook |
| Sheets | One | Many |
| Formatting and formulas | No | Yes |
| Data types | Everything is text | Numbers, dates, text |
| Opens in | Anything | Spreadsheet software |
Use CSV to exchange data between systems. Use XLSX when people need formatting, formulas or multiple sheets.
A practical example
The row name,quantity contains two fields. A value such as "Smith, Alex" needs surrounding quotes so its comma doesn’t create another column.
What to watch out for
CSV doesn’t preserve workbook sheets, cell styling or data types. Spreadsheet software may interpret postal codes as numbers and remove leading zeros, or read dates in the wrong order.
Tools you can use
- Clean CSV · Blank rows, duplicates and stray spaces out
- CSV to JSON · Rows to objects, quoted fields handled
- CSV to Excel · Keeps leading zeros and long IDs intact
- Split CSV · By row count, equal parts or column value
- Merge CSV · Combine files, matched by column name
- Excel to CSV · Every sheet, including old .xls files
Go a little deeper
- Combine CSV files without repeating headers
- CSV vs Excel: what is the difference?
- How to convert CSV to JSON
- How to open an .xls or .xlsx file without Excel
Common questions
Can I open a CSV file without Excel?
Yes. A CSV is plain text, so any text editor can open it, and Google Sheets, LibreOffice and Apple Numbers all import it as a table.
Why does Excel put all my CSV data in one column?
The file uses a different delimiter from the one Excel expects for your region, typically semicolons instead of commas. Import it and choose the delimiter explicitly.
Why did my leading zeros disappear?
The spreadsheet decided the column holds numbers and dropped the zeros. The CSV itself still contains them. Import the column as text to keep values such as 00123 intact.