SheetCompareHow to compare a XLS and a XLSX file
- 1
Drop both files
Drag your .xls file into the left zone and your .xlsx file into the right zone. SheetCompare auto-detects the format from the extension.
- 2
Match the headers
If column orders differ, SheetCompare matches columns by header name automatically. You can override the mapping if your files use different column names for the same data.
- 3
Read the diff
Added rows are green, removed rows are red, and changed cells are highlighted with the old value crossed out. Filter to show only changes.
XLS vs XLSX: the differences that actually matter
Most diff false-positives between XLS and XLSX come from one of these gaps. SheetCompare handles them so you don't see phantom changes.
| Property | XLS | XLSX |
|---|---|---|
| Full name | Excel 97–2003 Binary | Office Open XML Spreadsheet |
| Extension | .xls | .xlsx |
| Storage | Binary | Zipped XML |
| Stores formulas | ||
| Stores formatting | ||
| Multiple sheets | ||
| Human-readable | ||
| Streamable |
When XLS is the right format
Legacy Excel format used by Excel 97 through 2003. A proprietary binary stream (BIFF). Still common in enterprise systems that pre-date the 2007 XLSX switch.
- Legacy financial systems and SAP exports
- Banks, insurers, and government agencies on old toolchains
- Files received from partners still on Excel 2003
When XLSX is the right format
Modern Excel format. A ZIP archive of XML parts that stores values, formulas, formatting, multiple sheets, and metadata. The default save format in Excel 2007 and later.
- Financial models and analyst workbooks
- Reports shared with non-technical stakeholders
- Anything that needs formulas, charts, or formatting preserved
Frequently asked questions
Can I compare a XLS file against a XLSX file directly?▾
Yes. SheetCompare normalizes XLS and XLSX into the same row/column model after parsing, so a cross-format diff works the same as comparing two XLS files. Headers are matched by name, not position, so column order doesn't matter.
Do I need to convert XLS to XLSX (or back) before comparing?▾
No. Conversion before comparison is the most common source of false-positive diffs — type coercion and locale formatting silently change values. SheetCompare reads each format with the right parser and compares the underlying values directly.
Where are my files uploaded?▾
Nowhere. Both files are parsed and diffed entirely in your browser using JavaScript. The files never reach our servers, which is why you can compare confidential financial, payroll, or PII data without a vendor review.
What's the largest XLS or XLSX file I can compare?▾
The free tier handles files up to 5,000 rows each. Pro raises that to 100,000 rows per file. There's no row limit on Team — only your browser's available memory.
What's actually different between XLS and XLSX?▾
Excel 97–2003 Binary (.xls) is a binary format. Office Open XML Spreadsheet (.xlsx) is a zipped XML archive. The most common gotchas when crossing them are listed in the differences table above.