Microsoft Windows Retains Old File Naming Rules for Compatibility
Key files in Windows 11 continue to follow the MS-DOS era 8.3 file naming convention. Microsoft cites decades of compatibility requirements for this decision.
Microsoft continues to adhere to the legacy 8.3 file naming convention, originating from the MS-DOS era, within its latest Windows 11 operating system. Core system files such as kernel32.dll and ntoskrnl.exe still follow the rule of a maximum of eight characters before the file extension and three after. This practice is maintained primarily to ensure backward compatibility.
The 8.3 naming rule, which restricts file names to eight characters before the period and three characters after, was established during the MS-DOS period. Filenames were also limited to ASCII characters, disallowing spaces or multiple periods. While modern Windows components are no longer bound by these restrictions, older system files have been kept consistent.
According to Microsoft, altering these file names could break applications that rely on direct links to specific file names. This need for compatibility is the reason the old conventions have not been fully abandoned, even if they are no longer technically necessary. Support for long file names was not mandated across all systems even by Windows 95.
Long file names have historically introduced other compatibility challenges. Windows could automatically generate short aliases for long file names. For instance, if an installer attempted to copy shellstyle.dll to a folder already containing shellstuff.dll, the new file might be named SHELLS~2.DLL. Long file names became more standard only with Windows XP.