Format comparison
XLS vs XLSX
XLS is legacy binary Excel; XLSX is the modern default. Prefer XLSX for new work and convert old XLS archives when sharing.
Decision table
| Feature | XLS | XLSX |
|---|---|---|
| Era | Legacy | Modern |
| Structure | Binary BIFF | ZIP + XML |
| Best for | Old archives | All new workbooks |
| Row/feature limits | Older limits | Modern Excel limits |
| Cloud / Sheets | Import with care | Better |
| Recommended new saves | No | Yes |
Choose XLS when…
- Reading historical .xls files
- Migrating old finance shares
Choose XLSX when…
- New models and dashboards
- Sharing with modern Excel/Sheets
- Long-term workbook storage
Verdict
Open XLS for history, save XLSX going forward. Use CSV when you only need values for a pipeline.
Convert between them
Jump straight into a private browser converter — files are not uploaded to a server.
Keep exploring this topic
Stay inside the XLS / XLSX knowledge graph — sibling comparisons, best-format guides, and converters — not generic homepage links.
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