When you save a spreadsheet, Excel offers more than a dozen formats. LibreOffice and Google Sheets add a few more. For most people the choice is automatic: save with the default format and move on. But choosing the right format can save you compatibility, size, security and data loss problems. In this guide we go through the most common formats and when to use each one.
XLSX: today’s standard
Excel’s default format since 2007. It stores data in XML files compressed into a ZIP package.
- Advantages: lightweight, supports over a million rows, compatible with almost every program, does not run macros.
- Use it for: everyday work, sharing files with others, archiving documents.
XLS: the classic format
The binary format of Excel 97-2003.
- Advantages: compatible with very old systems.
- Drawbacks: limited to 65,536 rows and 256 columns, heavier files, can contain macros without warning.
- Use it for: only when a legacy system requires it. You can convert it to XLSX with our tool on the Excel tools page.
XLSM: macro-enabled workbooks
Identical to XLSX, but it can store VBA macros.
- Advantages: automation inside the workbook.
- Drawbacks: a security risk if the file comes from an unknown source; many companies block these files in email.
- Use it for: workbooks with trusted internal automation.
XLSB: modern binary
A binary format introduced with Excel 2007.
- Advantages: opens and saves very quickly, small size for very large workbooks.
- Drawbacks: less compatible with other programs and online tools.
- Use it for: huge workbooks used only in Excel.
CSV: pure data
A text file with values separated by commas or semicolons.
- Advantages: universal, opens in any program, ideal for imports and exports.
- Drawbacks: a single sheet, no formatting, no formulas, encoding and delimiter issues if you are not careful.
- Use it for: exchanging data between systems, importing products or contacts. Convert your workbooks with our Excel to CSV tool.
TSV: tab-separated values
Like CSV, but it uses the tab character as the separator.
- Advantages: avoids conflicts when data contains commas.
- Use it for: copying and pasting between applications and some data analysis workflows.
ODS: the open format
LibreOffice Calc’s native format, based on the OpenDocument standard.
- Advantages: an open international standard, free, preferred by many public bodies.
- Drawbacks: some advanced Excel features may change when converting.
- Use it for: working with free software or delivering documents to organizations that require it.
PDF: for reading, not calculating
Although it is not a spreadsheet format, it is the usual destination for reports and quotes.
- Advantages: fixed layout, not editable, opens on any device.
- Use it for: sharing final results. Convert with our Excel to PDF tool and, if you need the data back, use PDF to Excel.
Summary table
| Format | Max rows | Macros | Multiple sheets | Best use |
|---|---|---|---|---|
| XLSX | 1,048,576 | No | Yes | Everyday work |
| XLS | 65,536 | Yes | Yes | Legacy systems |
| XLSM | 1,048,576 | Yes | Yes | Automation |
| XLSB | 1,048,576 | Yes | Yes | Huge workbooks |
| CSV | No fixed limit | No | No | Data exchange |
| ODS | 1,048,576 | Yes (Basic) | Yes | Free software |
How to choose the right format
Ask yourself these questions:
- Who will open the file? If it is another person with Excel or Google Sheets, XLSX. If it is a system, probably CSV.
- Do you need to keep formulas and formatting? Then rule out CSV and TSV.
- Does the file have macros? Use XLSM and let the recipient know.
- Should it only be read? PDF.
- Is an open standard required? ODS.
Converting between formats
Changing formats is common and, in most cases, safe. Even so, always check the result, especially when moving to a format with fewer capabilities (for example, from XLSX to CSV or XLS). On our Excel tools page you will find free converters between XLS, XLSX, CSV, ODS and PDF, plus a comparison tool to verify nothing was lost.
Frequently asked questions
Which format does Google Sheets use?
Google Sheets stores sheets in its own cloud format, but lets you download them as XLSX, ODS, PDF, CSV, TSV and HTML. To share with Excel users, download as XLSX.
Does a CSV have a row limit?
The format itself has no limit, but the program you open it with does. Excel will only show 1,048,576 rows; if the CSV has more, you will need to split it or use a data analysis tool.
Is it dangerous to open an XLSM file?
It can be if it comes from an unknown source, because macros can run actions on your computer. Excel blocks macros by default; enable them only if you fully trust the sender.
Which format is best for long-term archiving?
To keep editable data, XLSX or ODS, both international standards. To preserve the exact look of a report, PDF, ideally the PDF/A variant designed for archiving.
Conclusion
Every spreadsheet format has its purpose: XLSX for daily work, CSV for exchanging data, ODS for free software, XLSM for automation, PDF for presenting and XLS only for compatibility. Choosing well from the start avoids unnecessary conversions and data loss. Keep this guide as a reference and use our tools whenever you need to move from one format to another.
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