robocopy, or "Robust File Copy", is a command-line directory replication command. It was available as part of the Windows Resource Kit, and introduced as a standard feature of Windows Vista and Windows Server 2008.
Robocopy is designed for reliable mirroring of directories or directory trees. It has features to ensure all NTFS attributes and properties are copied, and includes additional restart code for network connections subject to disruption.
Robocopy is notable for capabilities above and beyond the built-in Windows copy and xcopy commands, including the following:
- Ability to tolerate network outages and resume copying where it previously left off (incomplete files are noted with a date stamp corresponding to 1980-01-01 and contain a recovery record so Robocopy knows from where to continue).
- Ability to correctly copy attributes, owner information, alternate data streams, auditing information, and timestamps by default, without the need for numerous often forgotten command line switches.
- Ability to correctly copy NTFS ACLs, (when /COPYALL provided), and to assert the Windows NT "backup right" (/B) so an administrator may copy an entire directory, including files denied readability to the administrator.
- Persistence by default, with a programmable number of automatic retries if a file cannot be opened.
- A "mirror" mode, which keeps trees in sync by optionally deleting files out of the destination that are no longer present in the source.
- Ability to copy large numbers of files that would otherwise crash the built-in XCOPY utility.
- A progress indicator on the command line that updates continuously.
Notably, Robocopy cannot copy open files that are in use by other users or applications. The so-called Backup mode is an administrative privilege that allows Robocopy to override permissions settings (specifically, NTFS ACLs) for the purpose of making backups. The Windows Volume Shadow Copy service is the only Windows subsystem that can copy open files while they are in use. Robocopy does not implement accessing the Volume Shadow Copy service in any way, inhibiting its usefulness as a backup utility for volumes that may be in use. However, one can use separate utilities such as
DISKSHADOW (included with Windows Server 2008) to create a shadow copy of a given volume with which to backup using Robocopy.
On the other hand, by design, the original Robocopy version is not able to replicate security attributes of files which have had their security permissions changed after an initial mirroring.  This behavior was fixed on Robocopy versions included in Windows 2008 and Windows Vista. The downside of this approach is that it means Robocopy does not behave consistently between different platforms. 
Although Robocopy itself is a command-line tool, Microsoft Technet has also provided a GUI front-end, the GUI requires the .NET Framework 2.0. It has been developed by Derk Benisch, a systems engineer with the MSN Search group at Microsoft. Robocopy GUI also includes version XP026 of Robocopy (Vista version). When downloaded from the TechNet link below, the version reported is "Microsoft Robocopy GUI 3.1.2." When this version of RoboCopy is run, it then reports on its header: ROBOCOPY :: Robust File Copy for Windows :: Version XP026
Common usage examples
Copy directory contents recursively, all contents of foo to bar: robocopy C:\foo C:\bar /ECopy directory recursively (/E), and copy all file information (/COPYALL, equivalent to /COPY:DATSOU, D=Data, A=Attributes, T=Timestamps, S=Security=NTFS ACLs, O=Owner info, U=aUditing info), do not retry locked files (/R:0). Note directory Timestamps will not be reset if using a Robocopy version older than XP026: robocopy C:\foo C:\bar /COPYALL /E /R:0Mirror foo to bar, destroying any files in bar that are not present in foo (/MIR), copy files in restartable mode (/Z) in case network connection is lost: robocopy C:\foo \\backupserver\bar /MIR /Z
Folder copier, not file copier
The syntax of Robocopy is markedly different from that of standard copy commands, in that it only accepts the names of folders, not files, as its source and destination arguments. Names of files and wild-card designations (such as "
") are not acceptable as source or destination. Files may be selected or excluded using the optional filespec filtering argument. Filespecs can only refer to the filenames relative to the folders already selected for copying, and fully-qualified path names are not accepted.
For example, in order to copy the file foo.txt from directory c:\bar to c:\baz, one could use the following syntax: robocopy c:\bar c:\baz foo.txt
Partial list of command line switches
The following is a list of the more common command line options for Robocopy: 
/Z : Copy files in restartable mode. "Restartable" means Robocopy should write a recovery record inside an incomplete file so if the operation is interrupted or aborted, a future run of Robocopy can resume copying where the previous one left off, instead of starting over at the beginning. This is useful for reliably copying large files or many files over an unreliable network such as a VPN or the Internet. An incomplete file has the same file size as the complete file, and is noted with a date stamp in the file system being within 24 hours of 1980-01-01 00:00.
/COPYALL : Makes sure NTFS security information is copied. Equivalent to /COPY:DATSOU, where D=Data, A=Attributes, T=Timestamps, S=Security=NTFS ACLs, O=Owner info, U=aUditing info
/B : Opens files in backup mode. Backup mode allows files to be opened without security restrictions, but requires additional rights on both the source and destination systems.
/ZB : Use restartable mode; if access denied use backup mode.
- /MIR : Activates mirror mode, deleting any files in the destination that are not present in the source (equivalent to /E and /PURGE).
/E : Copies subdirectories, even empty ones (like XCOPY).
/M : Copies only files with the Archive attribute and reset it (like XCOPY /M option).
/MOV : Moves the files, removing them from the source folder.
/MOVE : Moves files AND dirs (folders) (delete from source after copying).
/MON:n : This will monitor and trigger a copy after n changes (and MOT minutes).
/MOT:n : This will set the minimum monitor interval (n minutes) before another copy is triggered.
/XA:attributes : Excludes files with any of the given attributes set. Example: /XA:H will skip copying any hidden files.
/XF filespec : Excludes files indicated by filespec. Wildcards are accepted. Example: /XF *.bak will skip copying any file with an extension of .bak.
/XD dirspec : Excludes directories indicated by dirspec by name/path. Wildcards work (i.e. /XD BKUP* skips copying all directories whose name starts with "BKUP", regardless of where in the source tree they are found).
/XC : Exclude changed files.
/XN : Exclude newer files.
/XO : Exclude older files (Please note that the Robocopy GUI (3.1.1) does not use this switch correctly, meaning it still copies older files over newer ones. Version 3.1.2 corrects this problem.)
/XX : Exclude extra files and directories.
/XL : Exclude lonely files and directories.
/IS : Include same files.
/IT : Include tweaked files (ie.: if one file has Archive attribute, while the other file has Archive and Read-only properties).
/XJ : Exclude junctions. When copying user accounts to another place in Windows Vista, it is important to exclude junctions. The junction in '\Users\...\AppData\Local' named 'Application Data' points to its parent folder, creating a loop which will break Robocopy. Furthermore, if a junction point is contained in a source disk which is mirrored using /MIR (or /E /PURGE) to a target disk, and a junction point from the source disk is copied to the target disk, it will "point to" your source disk, potentially resulting in modification of the contents of the source disk.
/R:n : Tells Robocopy to retry 'n' times before giving up in the event of error (default is 1 million).
/IPG:n : Tells Robocopy to pause 'n' milliseconds between packets for network transfers. Useful to preserve bandwidth on slow lines.
/L : SimuLates performing the copy without actually doing it, which is useful for testing a command line without being committed to the results.
/W:n : Wait time between retries (default is 30 seconds).
/PURGE : Deletes files no longer in the source location.
/MAXAGE:n : MAXimum file AGE - exclude files older than n days/date.
/MINAGE:n : MINimum file AGE - exclude files newer than n days/date.
(If n < 1900 then n = no of days, else n = YYYYMMDD date).
- /S : Copies subdirectories unless they are empty (like XCOPY).
/NDL : No directory list – do not log directory names.
/NS : No size – don't log file sizes.
/NC : No class – don't log file classes.
/X : Report all extra files, not just those selected.
/V : Produce verbose output, showing skipped files.
/TS : Include source file time stamps in the output.
/FP : Include full pathname of files in the output.
/NP : No progress – don't display % copied.
/ETA : Show estimated time of arrival of copied files.
/LOG:file.txt : Replace file.txt with the status of the run.
/LOG+:file.txt : Append the status of the run to file.txt.
/TEE : Output to console window, as well as the log file.
/NJH : No job header.
/NJS : No job summary.(See a full list here)
- /NFL : No file list – don't log file names.
- A new option in Vista (XP027) /EFSRAW : Copy any encrypted files using EFS RAW mode; is not available for XP (XP026).
- Robocopy will not copy folder timestamps from the source folder. Instead, it will use the current date and time when creating new folders. To match the timestamps to the original, another file utility must be used. This flaw has been addressed in version XP026 and the Windows Vista version of Robocopy (switch /DCOPY:T).
- Robocopy doesn't reliably copy short filenames.
- Copying files in restartable mode is much slower (about 6x over a network) than in normal or backup mode due to the necessary management overhead.
- Although version XP026 can now copy compressed files this causes heavy fragmentation.
- Backup mode cannot circumvent explicit NTFS deny ACL's if the copier isn't the objects' owner. (Error message: ERROR 5 (0x00000005) Copying NTFS Security to Destination Directory. Access denied.)You can overcome this error by just copying the data in the files with these Options setting: /COPY:DTinstead of the /COPYALL option
- Like most file copy programs robocopy does not make use of multithreading and overlapped, asynchronous, queued IO or ringbuffers to improve performance.
- Robocopy does not preserve Hardlinks
- Robocopy cannot copy files over FTP links
- XP010 - Bundled in the Windows 2003 resource kit
- XP026 - Downloaded with Robocopy GUI
- XP027 - Bundled with Windows Vista
- XP028 - Bundled with Windows Vista SP1 and Windows Server 2008
Notes and References
- http://www.zdnet.com.au/blogs/snorage/soa/Microsoft-s-Robocopy-compromise/0,2000064373,339291041,00.htm Microsoft's Robocopy compromise
- http://msmvps.com/blogs/martinzugec/archive/2008/03/03/ugly-bug-in-robocopy-ignoring-security-on-file-level.aspx Ugly bug in Robocopy - ignoring security on file level
- News: Joshua Hoffman. Utility Spotlight Robocopy GUI. html. TechNet Magazine. Microsoft Corporation and CMP Media, LLC. November, 2006. 2008-07-17.
- Robocopy.exe, Microsoft Windows Server 2003 Resource Kit, help output when run with /? command line switch. Complete help with /??? command line switch.