In short: Use a local parser instead of Excel automation to compare supported workbook formats.
Supported
XLSX and XLSM use the streaming workbook index. XLS and XLSB use a bounded compatibility path. CSV and TSV use streaming reads, including UTF-8 and CP949 decoding.
1. Select the previous and current files
Use the native file picker for each side. xlLens reads only paths selected by the user and never uploads workbook contents.
- Previous: the baseline workbook
- Current: the workbook you want to review
- Supported: XLSX, XLSM, XLS, XLSB, CSV, and TSV