XLSB files are unlikely to be supported, and the exception probably should give some indication that the file is not in a supported format. There appear to be a few ways to determine whether a file is XLSB (as opposed to XLSX or XLSM): 1) XLSB content types: - workbook application/vnd.ms-excel.sheet.binary.macroEnabled.main - sharedStrings application/vnd.ms-excel.sharedStrings - worksheet application/vnd.ms-excel.worksheet - styles application/vnd.ms-excel.styles 2) File extension: ".bin" for the workbook or worksheets is a good sign of an XLSB file. Looking at other open source projects: - python XLRD https://github.com/python-excel/xlrd raises an error if xl/workbook.bin is a file in the package - javascript js-xlsx https://github.com/SheetJS/js-xlsx runs XLSB parsers if the relevant files end with ".bin" - libreoffice has some information available at https://github.com/LibreOffice/core/blob/master/oox/source/dump/xlsbdumper.ini
As of r1615118, we now throw XLSBUnsupportedException, which extends from UnsupportedFileFormatException