These characters are forbidden in DOS/Windows file names and extensions:

< > : " / \ | ? *

These characters are allowed in DOS/Windows file names and extensions:


A file name is made up of: a base file name and an optional extension, separated by a period. Multiple periods may appear in a file name. Only the last period and the following extension designate the file type.

The MS-DOS FAT (FAT32) file system supports 8 characters for the base file name and 3 characters for the extension. This is known as an 8.3 file name. The FAT/FAT32 file system and the NTFS file system are not limited to 8.3 file names, today they support a long file name.

File Naming

The following rules enable applications to create and process valid names for files and directories regardless of the file system:

Allowed  Path Length

In  Windows , the maximum length for a path is 260 characters. A path is structured in the following order: drive letter, colon, backslash, components separated by backslashes, and a null-terminating character, for example, the maximum path on the D drive is D:\<256 chars>NUL.

The Unicode versions of several functions permit a maximum path length of approximately 32,000 characters composed of components up to 255 characters in length. To specify that kind of path, use the "\\?\" prefix.

For example, "\\?\D:\<path>". To specify such a UNC path, use the "\\?\UNC\" prefix. For example, "\\?\UNC\<server>\<share>". These prefixes are not used as part of the path itself. They indicate that the path should be passed to the system with minimal modification, which means that you cannot use forward slashes to represent path separators, or a period to represent the current directory. Also, you cannot use the "\\?\" prefix with a relative path. Relative paths are limited to MAX_PATH characters.

The shell and the file system may have different requirements. It is possible to create a path with the API that the shell UI cannot handle.



USB-Sticks use normally FAT32 file system. While transfering data from NTFS to FAT32 theoretically should be no problem, with bigger transfers of files with long file names there are always cases that files cannot get copied or are unreadable afterwards. This seems to be due to name clashes. So select always NTFS in USB-Stick format dialog. If NTFS doesn't show up in the dialog do the following:


Select Extension by starting letter:

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U -

V - W - X - Y - Z - OTHER - Allowed chars in Filenames - what is an extension?
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If you find an extension missing, write! No guaratee given for completeness or correctness. If you feel an extension is outdated, write!
Authors and retailers: it is in the interest of us all and our customers to avoid the double use of extensions! Please help us keep this compilation up to date!
Send extension data to: update@file-ext.4uj.org
Compilation Copyright (c) R.Cooper-Bitsch, visit: also: www.sunorbit.net