.xlsb

Excel Binary Workbook

Handled by macOS itself

Format facts

MIME type: application/vnd.ms-excel.sheet.binary.macroEnabled.12
Apple UTI: custom
Stock Quick Look: a ZIP-based container
Planned approach (census): native-sufficient
Icon hint: renders
Prevalence: common

Renderer note (from the census)

macOS handles this natively

Gotchas: binary records inside zip