Robocopy Basics

ROBOCOPY (Robust File Copy) is a command-line tool built into Windows since Vista/Server 2008 that replaces XCOPY for serious file transfer work. Unlike COPY or XCOPY, Robocopy automatically retries a file copy if it hits a transient error such as a network share momentarily dropping, waits between retries, and can resume large transfers without restarting from scratch, which makes it the standard choice for backup scripts and scheduled synchronization jobs in production environments.

The basic form is ROBOCOPY source destination [files] [options]. /E copies subdirectories including empty ones, /Z copies files in restartable mode so an interrupted large file transfer can resume instead of starting over, /R:n sets the number of retries on a failed file (default is one million, so scripts should always override it), and /W:n sets the seconds to wait between retries, so /R:3 /W:5 retries three times with a five-second pause is a common, script-friendly combination.

/E copies all files and subfolders (including empty ones) from source to destination but leaves any extra files already present at the destination untouched. /MIR, by contrast, makes the destination an exact mirror of the source: it copies new and changed files just like /E, but it also deletes any file or folder at the destination that no longer exists in the source. This makes /MIR extremely powerful for true synchronization but also dangerous, since pointing /MIR at the wrong destination folder can silently wipe out files that were never meant to be removed.

The /LOG:filename switch writes Robocopy's output to a file instead of (or in addition to, with /LOG+:filename to append) the console, which is essential for unattended scheduled tasks where no one is watching the screen. /MT:n enables multithreaded copying with n threads (default 8 when /MT is used without a number), which dramatically speeds up copying many small files over a network. Robocopy also returns a non-standard exit code: unlike most commands where 0 means success and non-zero means failure, Robocopy uses a bitmask where 0-7 all indicate some form of success and 8 or higher indicates a real failure, so scripts must check IF %ERRORLEVEL% GEQ 8 rather than the usual IF %ERRORLEVEL% NEQ 0.