Format guide
What is XLS?
Microsoft Excel 97–2003 Workbook is the older binary Excel workbook format replaced by XLSX in modern Office, created by Microsoft (1997+). XLS is legacy Excel. Convert to XLSX for current Excel/Sheets workflows, or to CSV when you only need values.
XLS format specifications
- Full name
- Microsoft Excel 97–2003 Workbook
- Kind
- legacy spreadsheet
- File extension
- .xls
- MIME type
- application/vnd.ms-excel
- Developer / standard
- Microsoft · 1997+
- Compression
- Binary BIFF (legacy)
- Quality model
- Lossless / not lossy
- Container
- No / single bitstream typical
- Common codecs
- —
- Technical sources
- —
- Transparency
- Not supported
- Animation
- No (still / non-animated typical use)
- Typical size
- Moderate; large sheets get unwieldy
- Browser support
- Not native — use Sheets/Excel Online after conversion
- Compatibility
- Excel and LibreOffice open most XLS files; prefer XLSX for sharing
XLS compression & quality
XLS uses the older BIFF binary structures. XLSX (ZIP+XML) is the modern default with better limits and interoperability.
Quality: Full spreadsheet in supporting apps; feature gaps vs modern Excel
Typical size: Moderate; large sheets get unwieldy
Transparency & animation
Not applicable.
Not applicable.
XLS metadata
Workbook properties and author fields; treat as sensitive if sheets hold personal data.
Best use cases for XLS
- Opening old finance archives
- Migrating to XLSX
- Legacy ERP exports
When to avoid XLS
- New models
- Very large modern datasets
- Cloud-first collaboration without conversion
Advantages
- Reads historical workbooks
- Still appears in older exports
Disadvantages
- Legacy format
- Row limits vs XLSX era
- Weaker cross-tool fidelity
- Security macro baggage
Compatibility
Excel and LibreOffice open most XLS files; prefer XLSX for sharing
Browsers: Not native — use Sheets/Excel Online after conversion
Software support
- Microsoft Excel
- LibreOffice Calc
- Google Sheets (import)
Device support
- Desktops with spreadsheet apps
How to open XLS
Open in Excel or LibreOffice Calc. Save as XLSX for modern sharing.
How to convert XLS
Convert XLS→XLSX for editing or XLSX→CSV for data pipelines using private converters when possible.
Popular XLS conversions
XLS comparison guides
Compare XLS with related formats to pick the right container for quality, size, and compatibility.
Related formats
XLS tools
Tools extend the format graph beyond one-off conversion — compression, metadata, and utilities for real workflows.
XLS FAQ
Is XLS the same as XLSX?
No. XLS is the older binary format; XLSX is Office Open XML and the current standard.
Are my XLS files uploaded on Format Convertly?
No. XLS conversion runs in your browser. Files are not sent to Format Convertly servers for processing.