Keep the original .xlsx file. Export a small sample to CSV and compare it with the values shown in the workbook before processing a larger sheet.
What the tools read
The browser opens the XLSX ZIP package, reads supported worksheet XML and shared strings, and uses stored cell values. The supported upload size is limited to 10 MiB, with additional decompression and row limits. Results depend on whether usable cached values exist.
What the tools do not reproduce
Formulas are not calculated. A formula cell may have a cached result, an outdated result or no cached value at all. Styles, charts, comments, hyperlinks, pivot structures, workbook macros, external connections and protections are not carried over into cleaned files. The CSV-to-XLSX converter writes a new single-sheet workbook with text-only cell values.
Not supported
Legacy binary XLS, XLSB, encrypted or password-protected workbooks, full workbook round-trip editing and arbitrary locale-specific numeric interpretation are not supported. A file with an .xlsx extension is not necessarily a valid XLSX package.
How to verify the result
- Open the source workbook in a trusted spreadsheet application and check the relevant worksheet.
- Run the XLSX Sheet Inspector and verify the selected worksheet and row count.
- Export a sample to CSV using the XLSX-to-CSV tool and check special characters, empty cells and identifiers with leading zeros.
- Confirm values against the source, particularly formula-derived dates, totals and currencies.
- Save output as a new file and import it into the destination system for review.
If a workbook contains no cached value or has damaged XML, DataCleaner cannot reconstruct calculations or deleted information. Use a backup or a full spreadsheet application for recovery.
Related resources
Convert XLSX to CSV safely · Check formulas and sheets · Supported formats