CSV vs XLSX — Plain Data vs Rich Spreadsheet Format

CSV (Comma-Separated Values) and XLSX (Excel Open XML Spreadsheet) both store tabular data, but they are designed for completely different purposes.

CSV:

• Plain text — every value separated by commas, one row per line
• No formatting, no formulas, no charts, no multiple sheets
• Opens in every spreadsheet, database, code editor, and programming language without conversion
• Perfect for data exchange between systems

XLSX:

• Full spreadsheet workbook with multiple sheets, formulas, charts, conditional formatting, pivot tables, and macros
• Requires Excel or compatible software (Google Sheets, LibreOffice Calc)
• Formatting is preserved — fonts, colours, borders, number formats
• Appropriate for data analysis and reporting

File size: CSV is always smaller than XLSX for equivalent data, because XLSX includes formatting, formula, and structure overhead.

Use CSV when:

• Exporting data from a database, CRM, or web platform for import elsewhere
• Sharing data with a developer or data analyst
• The data is simple rows and columns with no formulas needed
• Maximum compatibility across all tools is required

Use XLSX when:

• You need formulas, pivot tables, or charts
• Multiple worksheets are needed
• Data needs formatting (currency, percentages, dates) preserved visually
• Sharing a report rather than raw data

Converting between them: XLSX → CSV loses all formatting and formulas. CSV → XLSX adds no formulas but makes data available for Excel functions. Always keep the source format when in doubt.