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.xls

High risk

Microsoft Excel 97-2003 Workbook

The pre-2007 binary Excel format. Still emitted by legacy enterprise systems and a classic malware delivery vector because of VBA macros.

MIME types

  • application/vnd.ms-excel

Category

document

What opens this file

  • Excel
  • LibreOffice Calc
  • Google Sheets
  • Numbers

How to open by OS

Windows

  • Excel, LibreOffice Calc.

Mac

  • Excel for Mac, LibreOffice Calc, Numbers.

Linux

  • LibreOffice Calc.

Ios

  • Excel Mobile, Numbers.

Android

  • Excel Mobile, Google Sheets.

Safety notes

  • xls can embed VBA macros and is still used by Emotet-era campaigns. Do not disable Protected View for unexpected files.
  • Legacy DDE links can trigger external command execution — another common payload mechanism.

Common mistakes

  • Maximum 65,536 rows — overflow breaks the file. Save as xlsx instead.
  • Files labelled .xls are sometimes actually CSV or HTML. Verify real bytes with the File Signature Checker.

Related extensions

References