What changes when Excel becomes CSV
CSV is plain text: one line per row, with values separated by a character. That makes it readable by almost any program, but it can only hold values. Converting keeps your data and drops everything else:
- Formulas become their calculated results.
- Formatting — colours, fonts, column widths, merged cells — is removed. A merged cell's value stays in its top-left cell.
- Each sheet becomes a separate file, because CSV has no concept of sheets.
- Numbers and dates are written as they're displayed in Excel, so 0.5 formatted as 50% exports as 50%.
- Charts, images and comments are not included.
Comma, semicolon or tab?
Comma is the standard and what most software, databases and import screens expect. Semicolon is the default in much of Europe and South America, where the comma is the decimal separator — if Excel opens your CSV with everything squeezed into column A, the file and your Excel disagree about the separator. Tab-separated output (saved as .tsv) is the safest choice when your values themselves contain commas, such as addresses.
Keeping accents and non-English characters
The CSV is saved as UTF-8, which can represent any character. Excel on Windows, however, assumes an older encoding unless the file starts with a byte-order mark (BOM), and shows é as é without it. The BOM option is on by default for that reason. Turn it off if the CSV is going into a program or script that doesn't expect one.
Leading zeros and long numbers
Values such as ZIP codes (02134), phone numbers and account IDs are exported exactly as displayed, zeros included. The problem usually appears when the CSV is opened again in Excel, which converts them back to numbers. To keep them, import the CSV through Data → From Text/CSV and set those columns to Text instead of double-clicking the file.