Why does the 260 character path length limit exist in Windows

Question

I have come up against this problem a few times at inopportune moments    Trying to work on open source Java projects with deep paths Storing deep Fitnesse wiki trees in source control An error trying to use Bazaar to import my source control tree   Why does this limit exist    Why hasn t it been removed yet     How do you cope with the path limit   And no  switching to Linux or Mac OS X is not a valid answer to this question

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You can mount a folder as a drive  From the command line  if you have a path C  path to long folder you can map it to drive letter X  using   subst x   path to long folder

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The question is why does the limitation still exist  Surely modern Windows can increase the side of MAX PATH to allow longer paths   Why has the limitation not been removed    The reason it cannot be removed is that Windows promised it would never change    Through API contract  Windows has guaranteed all applications that the standard file APIs will never return a path longer than 260 characters   Consider the following correct code   WIN32 FIND DATA findData   FindFirstFile  C  Contoso     ref findData     Windows guaranteed my program that it would populate my WIN32 FIND DATA structure   WIN32 FIND DATA      DWORD    dwFileAttributes     FILETIME ftCreationTime     FILETIME ftLastAccessTime     FILETIME ftLastWriteTime              TCHAR    cFileName MAX PATH               My application didn t declare the value of the constant MAX PATH  the Windows API did  My application used that defined value   My structure is correctly defined  and only allocates 592 bytes total  That means that i am only able to receive a filename that is less than 260 characters  Windows promised me that if i wrote my application correctly  my application would continue to work in the future    If Windows were to allow filenames longer than 260 characters then my existing application  which used the correct API correctly  would fail   For anyone calling for Microsoft to change the MAX PATH constant  they first need to ensure that no existing application fails  For example  i still own and use a Windows application that was written to run on Windows 3 11  It still runs on 64-bit Windows 10  That is what backwards compatibility gets you   Microsoft did create a way to use the full 32 768 path names  but they had to create a new API contract to do it  For one  you should use the Shell API to enumerate files  as not all files exist on a hard drive or network share    But they also have to not break existing user applications  The vast majority of applications do not use the shell api for file work  Everyone just calls FindFirstFile FindNextFile and calls it a day

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Another way to cope with it is to use Cygwin  depending on what do you want to do with the files  i e  if Cygwin commands suit your needs   For example it allows to copy  move or rename files that even Windows Explorer can t  Or of course deal with the contents of them like md5sum  grep  gzip  etc   Also for programs that you are coding  you could link them to the Cygwin DLL and it would enable them to use long paths  I haven t tested this though

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This is not strictly true as the NTFS filesystem supports paths up to 32k characters  You can use the win32 api and        prefix the path to use greater than 260 characters     A detailed explanation of long path from the  Net BCL team blog  A small excerpt highlights the issue with long paths     Another concern is inconsistent behavior that would result by exposing long path support  Long paths with the      prefix can be used in most of the file-related Windows APIs  but not all Windows APIs  For example  LoadLibrary  which maps a module into the address of the calling process  fails if the file name is longer than MAX PATH  So this means MoveFile will let you move a DLL to a location such that its path is longer than 260 characters  but when you try to load the DLL  it would fail  There are similar examples throughout the Windows APIs  some workarounds exist  but they are on a case-by-case basis

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From Windows 10  you can remove the limitation by modifying a registry key      Tip  Starting in Windows 10  version 1607  MAX PATH limitations have been removed from common Win32 file and directory functions  However  you must opt-in to the new behavior       A registry key allows you to enable or disable the new long path behavior  To enable long path behavior set the registry key at HKLM SYSTEM CurrentControlSet Control FileSystem LongPathsEnabled  Type  REG DWORD   The key s value will be cached by the system  per process  after the first call to an affected Win32 file or directory function  list follows   The registry key will not be reloaded during the lifetime of the process  In order for all apps on the system to recognize the value of the key  a reboot might be required because some processes may have started before the key was set    The registry key can also be controlled via Group Policy at Computer Configuration  gt  Administrative Templates  gt  System  gt  Filesystem  gt  Enable NTFS long paths    You can also enable the new long path behavior per app via the manifest    lt application xmlns  urn schemas-microsoft-com asm v3  gt       lt windowsSettings xmlns ws2  http   schemas microsoft com SMI 2016 WindowsSettings  gt           lt ws2 longPathAware gt true lt  ws2 longPathAware gt       lt  windowsSettings gt   lt  application gt

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It does  and it is a default for some reason  but you could easily override it with this registry key    HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control FileSystem   LongPathsEnabled  dword 00000001   See  https   blogs msdn microsoft com jeremykuhne 2016 07 30 net-4-6-2-and-long-paths-on-windows-10

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You can enable long path names using PowerShell    Set-ItemProperty -Path  HKLM  SYSTEM CurrentControlSet Control FileSystem  -Name LongPathsEnabled -Type DWord -Value 1    Another Version is to use a Group Policy in Computer Configuration Administrative Templates System Filesystem

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As to why this still exists - MS doesn t consider it a priority  and values backwards compatibility over advancing their OS  at least in this instance    A workaround I use is to use the  short names  for the directories in the path  instead of their standard  human-readable versions  So e g  for C  Program Files  I would use C  PROGRA 1   You can find the short name equivalents using dir  x

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Quoting this article https   docs microsoft com en-us windows desktop FileIO naming-a-file maximum-path-length-limitation     Maximum Path Length Limitation      In the Windows API  with some exceptions discussed in the following paragraphs   the maximum length for a path is MAX PATH  which is defined as 260 characters  A local path is structured in the following order  drive letter  colon  backslash  name components separated by backslashes  and a terminating null character  For example  the maximum path on drive D is  D  some 256-character path string lt NUL   where   lt NUL   represents the invisible terminating null character for the current system codepage   The characters  lt    are used here for visual clarity and cannot be part of a valid path string     Now we see that it is 1 2 256 1 or  drive      path  null    260  One could assume that 256 is a reasonable fixed string length from the DOS days  And going back to the DOS APIs we realize that the system tracked the current path per drive  and we have 26  32 with symbols  maximum drives  and current directories    The INT 0x21 AH 0x47 says    This function returns the path description without the drive letter and the initial backslash     So we see that the system stores the CWD as a pair  drive  path  and you ask for the path by specifying the drive  1 A  2 B        if you specify a 0 then it assumes the path for the drive returned by INT 0x21 AH 0x15 AL 0x19  So now we know why it is 260 and not 256  because those 4 bytes are not stored in the path string   Why a 256 byte path string  because 640K is enough RAM

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As to how to cope with the path size limitation on Windows - using 7zip to pack  and unpack  your path-length sensitive files seems like a viable workaround  I ve used it to transport several IDE installations  those Eclipse plugin paths  yikes   and piles of autogenerated documentation and haven t had a single problem so far    Not really sure how it evades the 260 char limit set by Windows  from a technical PoV   but hey  it works    More details on their SourceForge page here        NTFS can actually support pathnames up to 32 000 characters in   length        7-zip also support such long names       But it s disabled in SFX code  Some users don t like long paths  since   they don t understand how to work with them  That is why I have   disabled it in SFX code    and release notes      9 32 alpha     2013-12-01         Improved support for file pathnames longer than 260 characters          4 44 beta      2007-01-20         7-Zip now supports file pathnames longer than 260 characters       IMPORTANT NOTE  For this to work properly  you ll need to specify the destination path in the 7zip  Extract  dialog directly  rather than dragging  amp  dropping the files into the intended folder  Otherwise the  Temp  folder will be used as an interim cache and you ll bounce into the same 260 char limitation once Windows Explorer starts moving the files to their  final resting place   See the replies to this question for more information

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One way to cope with the path limit is to shorten path entries with symbolic links   For example    create a C  p directory to keep short links to long paths mklink  J C  p foo C  Some Crazy Long Path foo add C  p foo to your path instead of the long path

[windows] Why does the 260 character path length limit exist in Windows?

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