CSV is a plain text file that stores one table of values separated by commas. XLSX is Excel's workbook format: a compressed package that can hold many sheets, formulas, formatting and charts. Use CSV to move data between systems and XLSX to work with that data and present it to people.
The differences go further than formatting, and choosing the wrong format can cost you leading zeros, formulas or hours of cleanup. Here is how the two compare and when to use each.
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Key takeaways
- CSV holds raw values in one table; XLSX holds typed cells, many sheets, formulas, styles and charts.
- CSV is the safer format for imports, databases and version control because any program can read it.
- XLSX is better for reports, shared spreadsheets and anything with formulas or formatting.
- Converting between them is quick, so keep the format each step of your workflow needs.
Steps shown in the video
- Click Choose CSV Files and select your CSV
- Your file is listed with its size
- Click Convert to Excel to create the workbook
- Download your .xlsx file
What is a CSV file?
A CSV (comma-separated values) file is plain text. Each line is a row, and a delimiter, usually a comma, separates the values. The common rules for quoting and line breaks are written down in RFC 4180. You can open a CSV in any text editor.
order_id,customer,country,total
00742,"Dupont, Marie",FR,129.90
00743,Sam Lee,US,45.00What is an XLSX file?
XLSX is the default Excel format since Excel 2007. It is a ZIP package of XML files based on the Office Open XML standard. Each cell has a type (number, text, date, formula), and the package can store several worksheets, styles, charts, filters and data validation.
CSV vs XLSX: side-by-side comparison
| CSV | XLSX | |
|---|---|---|
| File type | Plain text | Compressed XML package |
| Sheets | One table | Many worksheets |
| Data types | Everything is text until a program interprets it | Numbers, text, dates, booleans, formulas |
| Formatting, charts, formulas | Not supported | Supported |
| Rows per sheet | No format limit | 1,048,576 rows, 16,384 columns |
| Opens in | Any spreadsheet, database, text editor or script | Excel, Google Sheets, LibreOffice, Numbers |
| Version control | Line-by-line diffs work | Binary diffs only |
| Typical risk | Excel misreads values on open | Hard for other systems to import |
The row limit comes from Microsoft's Excel specifications and limits. A CSV has no limit of its own, but you cannot open more rows in Excel than one sheet allows.
When should you use CSV?
- Importing data into a CRM, an online shop, an email tool or a database. Most import screens ask for CSV.
- Exchanging data between programs that do not share a format.
- Large datasets that exceed Excel's row limit.
- Data in version control, where you want readable line-by-line changes.
- Feeding scripts and APIs. For web apps, CSV to JSON is often the next step.
When should you use XLSX?
- Reports and dashboards with formatting, totals and charts.
- Shared spreadsheets where colleagues edit, filter and comment.
- Workbooks with formulas that must keep calculating.
- Several related tables that belong in one file as separate sheets.
- Data with leading zeros or long IDs, which stay safe once stored as text cells.
How to convert between CSV and XLSX
To go from CSV to a workbook, use CSV to Excel: it detects the delimiter and keeps leading zeros. To export a workbook for an import screen, use Excel to CSV. Remember that a CSV keeps only values, so formulas, formatting and extra sheets do not survive that direction.
Seeing odd results after opening a CSV in Excel? Read why a CSV opens in one column and how to fix it.
CSV vs XLSX: FAQ
Is CSV the same as Excel?
No. CSV is a plain text format that Excel can open. XLSX is Excel's own workbook format, which stores data types, formulas, formatting and several sheets.
Which is smaller, CSV or XLSX?
It depends on the data. XLSX is compressed, so a large table is often smaller as XLSX than as CSV, while a small table can be smaller as CSV.
Does CSV keep formulas?
No. A CSV stores the calculated values only. Keep an XLSX copy if you need the formulas.
Can a CSV have more than one sheet?
No. A CSV holds one table. Export each sheet to its own CSV file.
Which format should I use for importing data?
CSV, in most cases. Import tools almost always accept it, and it carries no formatting that could confuse the import.
Use both, at the right moment
CSV is the format for moving data and XLSX is the format for working with it. Keep raw exports as CSV, convert to XLSX when people need to read or edit them, and convert back when another system needs the data.
