Maximum filename lengths vary by operating system. Mac OS X, for example, supports filenames up to a 255 character limit. In Windows Vista and Windows 7, the combined length of a filename and path has a maximum of 260 characters.
In Windows Vista and 7, the maximum length of a filename depends on its path. This is because the combined path and filename, such as "C:Program Filesfilename.txt" has a maximum allowable length of 260 characters. As a result, errors sometimes occur when trying to copy a file to a different path of longer length.
In Mac OS X, up to 255 characters are supported; however, Apple notes that non-English characters such as Chinese and Korean symbols may take up to 9 characters worth of space. Mac OS 9 and earlier only supported up to a 31 character length.