1. 01Open an XLSX, XLS or CSV file; if a CSV comes out as mojibake, switch to GBK and parse it again.
2. 02Move between worksheets, search the current sheet, click a column header to sort, and page through 100 rows at a time.
3. 03Export the current sheet as CSV or JSON, or write every worksheet back out as a single XLSX workbook.

CSV export always uses UTF-8 with a BOM and CRLF line endings; JSON takes the first row as the key names and turns every following row into an object; XLSX reassembles all parsed sheets into a new workbook.

• Only the .xlsx, .xls and .csv extensions are accepted.
• CSV encoding choices are limited to UTF-8 and GBK; the automatic mojibake hint is only a heuristic.
• The first row is treated as the header, and empty sheets, duplicated headers or complex Excel cells may not carry the same meaning as in the original workbook.
• Formulas, macros, styling and external links are not a fidelity target for this viewer; exporting rebuilds data rather than preserving the original file losslessly.
• Search and sorting act only on the local data of the current worksheet.

Workbooks, CSV contents and exported data are all handled locally in the browser and are never sent to a third party.