FreeFileSync User Manual:
— Folder Comparison and Synchronization —
- Choose left and right folders.
- Compare them.
- Select synchronization settings.
- Press Synchronize to begin synchronization.
For more detailed explanations on how to set up the most common synchronization scenarios,
have a look at the FreeFileSync video tutorials
Main Dialog Overview
- Start comparison
- Change comparison settings
- Include/exclude specific files
- Change synchronization settings
- Start synchronization
- Add folder pairs
- Select left and right folders
- Save/load configuration
- Tree overview panel
- Synchronization preview
- Select categories to show on grid
- Synchronization statistics
Command Line Usage
FreeFileSync supports additional synchronization scenarios via a command line interface.
To get a syntax overview, open the console, go to the directory where FreeFileSync is installed and type:
FreeFileSync.exe -h or FreeFileSync.exe --help
1. Run a FreeFileSync batch job
In order to start synchronization in batch mode, supply the path of a ffs_batch configuration file as the first argument for FreeFileSync.exe:
FreeFileSync.exe "D:\Backup Projects.ffs_batch"
After synchronization one of the following status codes is returned:
0 - Synchronization completed successfully
1 - Synchronization completed with warnings
2 - Synchronization completed with errors
3 - Synchronization was aborted
You can evaluate these codes from a script (e.g. a cmd or bat file on Windows)
and check if synchronization completed successfully:
"C:\Program Files\FreeFileSync\FreeFileSync.exe" "D:\Backup Projects.ffs_batch"
if errorlevel 1 (
::if return code is 1 or greater, something went wrong, add special treatment here
echo Errors occurred during synchronization...
Instead of showing an error message, you can also send an email notification (using a third party tool).
If you are running the batch job unattended, make sure your script is not blocked showing a notification dialog. Consider the
following options when setting up the FreeFileSync batch job:
- Enable Auto-Close to skip the summary dialog after synchronization.
- Set up error handling to Ignore errors or Cancel to stop the synchronization at the first error.
2. Start a FreeFileSync GUI configuration
If you pass a ffs_gui file, FreeFileSync will start in GUI mode and immediately start comparison (but only if all directories exist):
FreeFileSync.exe "D:\Manual Backup.ffs_gui"
3. Customize an existing configuration
You can replace the directories of a given ffs_gui or ffs_batch configuration file by using the -DirPair
FreeFileSync.exe "D:\Manual Backup.ffs_gui" -dirpair C:\NewSource D:\NewTarget
4. Merge multiple configurations
When more than one configuration file is provided, FreeFileSync will merge
everything into a single configuration with multiple folder pairs and start in GUI mode:
FreeFileSync.exe "D:\Manual Backup.ffs_gui" "D:\Backup Projects.ffs_batch"
5. Use a different GlobalSettings.xml file
By default, FreeFileSync uses a single GlobalSettings.xml file containing options that apply to all synchronization tasks;
for examples see Expert Settings
If you want FreeFileSync to use a different settings file instead, you can specify the path via command line:
FreeFileSync.exe "D:\My GlobalSettings.xml"
When comparing two folders, FreeFileSync analyses the paths relative to the left and right base folders
of the contained files.
If the relative path matches, FreeFileSync decides how the file pair is categorized by considering the selected comparison variant:
1. Compare by File time and size
This variant considers two files equal when both modification time and file size
It should be selected when synchronizing files with a backup location.
Whenever a file is changed, its file modification time is also updated.
Therefore, a comparison by File Time and size
will detect all files that should be synchronized.
The following categories are distinguished:
2. Compare by File content
- file exists on one side only
- file exists on both sides
- different date
- same date
- conflict (same date, different size)
Two files are marked as equal if they have identical content
This variant should be selected when doing consistency checks to see if the files on both sides are bit-wise identical.
Naturally, it is the slowest of all comparison variants, so its usefulness for the purpose of synchronization is limited.
If used for synchronization, it can serve as a fallback when modification times are not reliable. For example
certain mobile phones and legacy FTP servers do not preserve modification times, so the only way to detect different files when the
file sizes are the same is by reading their content.
3. Compare by File size
- file exists on one side only
- file exists on both sides
Two files are considered equal if they have the same file size
Since it's possible for files that have the same size to have different content, this variant should only be used when file modification times are not
available or reliable, e.g. in certain MTP and FTP synchronization scenarios, and where a comparison by content would be too slow.
- file exists on one side only
- file exists on both sides
Symbolic Link Handling
FreeFileSync lets you choose to include symbolic links (also called symlinks or soft links)
when scanning directories rather than skipping over them. When included, you can select between two ways to handle them:
Treat symbolic links like the object they are pointing to. Links
pointing to directories are traversed like ordinary directories and
the target of each link is copied during synchronization.
Evaluate the symbolic link object directly. Symbolic links will be shown as separate entities.
Links pointing to directories are not traversed and the link object itself
is copied during synchronization.
- Under Windows the symbolic link options apply to symbolic links, volume mount points and NTFS junction points.
- Copying symbolic links requires FreeFileSync to be started with administrator rights.
Daylight Saving Time (Windows)
A common problem synchronization software has to handle is +-1 hour
file time shifts after a Daylight Saving Time (DST) switch has
occurred. This can be observed, for example, when a FAT32- or exFAT-formatted
volume (in the following called "FAT") is compared against an NTFS volume,
like when synchronizing a USB memory stick against a local disk.
Files that previously appeared to be in sync are
now shown with a one hour modification time offset, although they
have not been modified by the user or the operating system.
The reason for this behavior lies in the way NTFS and FAT
store file times: NTFS stores time in UTC format, while FAT uses
When times of these two different formats are compared, one format
has to be converted into the other first. In either way, Windows uses
the current DST status as well as the current time zone for
its calculations. Consequently, the result of this comparison is
dependent from current system settings with the effect that file times
that used to be the same show up as different after a DST switch or when the time zone has changed.
For a detailed discussion about this issue see:
- In FreeFileSync's comparison settings you can enter one or more time shifts to ignore during comparison:
If you need to handle differences due to daylight saving time, enter a single one hour shift.
If the differences are caused by changing the time zone, enter one or more time shifts as needed.
File times have to be equal or differ by exactly the time shift entered to be considered the same.
Therefore, the time shift setting should not be confused with a time interval or tolerance.
- Alternatively, you can avoid the problem in the first place by only synchronizing from FAT to FAT or NTFS to NTFS file systems.
Since most local disks are formatted with NTFS and USB memory sticks with FAT, this situation could be handled by formatting the USB stick with NTFS as well.
Exclude Items via Filter
Files and directories are only considered for synchronization if they pass
all filter rules. They have to match at least one
entry in the
include list and none
of the entries in the exclude list as presented in the filter configuration dialog:
- Each list item must be a file or directory path relative to synchronization base directories.
- Multiple items must be separated by | or a new line.
- Wild cards * and ? may be used: * means zero or more characters while ? represents exactly one character.
Example: Exclude items from folder pair C:\Source, D:\Target
|Single file C:\Source\file.txt
|Single folder C:\Source\SubFolder
|All files (and folders) named thumbs.db
|All *.tmp files located in SubFolder
|Files and folders containing temp somewhere in their path
|Multiple entries separated by vertical bar
||*.tmp | *.doc | *.bak
|All subdirectories of the base directories
|*.txt files located in subdirectories of base directories
Example: Exclude a sub folder except for certain files
Set up two folder pairs
with the same source and target paths but with distinct local filters
Folder pair 1; local exclude
Folder pair 2; local include
Example: Exclude empty folders
Set up a file size filter
with a lower limit of 0 bytes
. Both the time span
and file size
filters match files only, so this will exclude all folders.
During synchronization however some excluded folders will still be synchronized if they contain at least one non-excluded item, i.e. when they are not empty.
- For simple exclusions, just right-click and exclude one item or a list
of items directly via the context menu on main dialog.
- A filter phrase is compared against
both file and directory paths. If you want to consider directories
only, you can give a hint by appending a path separator.
- Both slash (/) and backslash (\) can be used as the path separator character.
FreeFileSync has a number of special-purpose settings that can only be accessed
by manually opening the global configuration file GlobalSettings.xml
Note that this file is read once when FreeFileSync starts and saved again on exit.
Therefore, you should apply manual changes only while FreeFileSync is not running.
For the portable FreeFileSync variant the file is found in the installation folder,
for local installations go to:
|macOS: ||~/Library/Application Support/FreeFileSync|
<?xml version="1.0" encoding="UTF-8"?>
Contents of GlobalSettings.xml
By default file modification times
are allowed to have a 2 second difference while still being
considered equal. This is required by FAT/FAT32 file systems which
store file times only with a 2-second precision.
While synchronization is running, other applications that are accessing the same
data locations may experience a noticeable slowdown. Enable this
setting to lower FreeFileSync's resource consumption at the cost of a
significantly slower synchronization speed.
In order to prevent multiple synchronization tasks from reading and writing the same files,
FreeFileSync instances are serialized with lock files (sync.ffs_lock
The lock files are only recognized by FreeFileSync and make sure that at most,
a single synchronization is running against a certain folder at a time while
other instances are queued to wait.
This ensures that only consistent sets of files are subject to synchronization.
The primary use case are network synchronization scenarios where
multiple users run FreeFileSync concurrently against a shared network folder.
If active, FreeFileSync will binary-compare source and target files after
copying and report verification errors. Note that this may double
file copy times and is no guarantee that data has not already been
corrupted prior to copying. Additionally, corruption may be hidden by
deceptively reading valid data from various buffers in the
application and hardware stack:
the CopyFile function verify that the data reached its final destination successfully?
When you double-click on one of the rows on the main dialog, FreeFileSync opens the operating system's file browser
by default. On Windows, it calls explorer /select, "%local_path%"
Linux xdg-open "%parent_path%"
and on macOS open -R "%local_path%"
To customize this behavior or integrate other external applications into FreeFileSync,
navigate to Menu → Tools → Options → Customize context menu
and add or replace a command.
The first entry
will be executed when double-clicking
a row on the main grid or when pressing ENTER
All other entries can be accessed quickly by pressing the associated numeric keys
or via the context menu that is shown after a right mouse click.
In addition to regular Macros
, the following special macros are available:
|Full file or folder path
|Creates a temporary local copy for files located on SFTP and MTP storage. Identical to %item_path% for files on local disks and network shares.
|File or folder name
|Parent folder path
To refer to the item on the opposite side, append "2
" to the macro name: e.g.
- Start file content comparison tool (WinMerge):
"C:\Program Files (x86)\WinMerge\WinMergeU.exe" "%local_path%" "%local_path2%"
opendiff on macOS (requires Xcode):
opendiff "%local_path%" "%local_path2%"
- Show file in Windows Explorer:
explorer /select, "%local_path%"
- Open file with associated application:
- Open Command Prompt for selected item:
cmd /k cd /D "%parent_path%"
- Copy item path to Clipboard (as alternative to CTRL + C)
cmd /c echo %item_path%| clip
- Write list of selected file paths to a text file:
cmd /c echo %item_path% >> %csidl_Desktop%\file_list.txt
- Preview files using Quick Look on macOS:
qlmanage -p "%local_path%"
Macros need to be protected with quotation marks if they can resolve to file paths containing whitespace characters.
All directory paths may contain macros that are expanded during
synchronization. The beginnings and ends of each macro are marked by a %
character. In addition to special macros
handling time and date, the operating system's environment variables
may also be used.
||day of the week
||[01–52] calendar week
Environment variables (Windows)
||C:\Program Files (x86)
Special folder locations (Windows)
||C:\Users\Zenju\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch
Note: Most of the above macros also have a variant for public folders, e.g.
%csidl_Documents% has %csidl_PublicDocuments%.
You can add flexibility to an ffs_batch configuration file
by creating new temporary environment variables in a bat or cmd file that are evaluated by FreeFileSync at runtime:
The FreeFileSync batch file C:\SyncJob.ffs_batch
instead of an absolute target folder and is invoked by a cmd file:
"C:\Program files\FreeFileSync\FreeFileSync.exe" C:\SyncJob.ffs_batch
::%MyVar% is resolved as C:\Target during synchronization
Temporary environment variables created with the set command are only valid if the synchronization is started by calling the
FreeFileSync executable directly. Using start /wait would create a new program context without these temporary variables.
FreeFileSync can be set up to issue multiple file accesses
in parallel. This speeds up synchronization times dramatically in
cases where single I/O operations have significant latency
(e.g. long response times on a slow network connection)
or they cannot use the full bandwidth available
(e.g. an SFTP server that has a speed limit for each connection).
The number of parallel file operations that FreeFileSync should use
can be set up for each device individually
in the Comparison Settings
It is evaluated for all folder pairs of a configuration as follows:
- During comparison FreeFileSync groups all folders by their root devices.
For example, consider a configuration with two folder pairs and parallel file operations set up:
FreeFileSync will put the folders C:\Source and
into the same group and allow only 1 file operation at a time.
Folder D:\Target will be traversed using 2 operations,
and E:\Target using 3 operations at a time.
In total FreeFileSync will be scanning all four folders
employing 6 file operations in parallel.
|C:\Source ||↔ ||D:\Target|
|C:\Source2 ||↔ ||E:\Target|
- When synchronizing a folder pair FreeFileSync
will use the maximum of the number of parallel operations
that the two folders support.
In the previous example the folder pair
C:\Source ↔ D:\Target
will be synchronized using 2 parallel operations, and
C:\Source2 ↔ E:\target
will be using 3.
FreeFileSync implements parallel file operations by opening multiple connections to a device.
Some devices like SFTP servers have limits on how many connections they allow and will
fail if too many are attempted; see (S)FTP Setup
— Automated Synchronization —
The primary function of RealTimeSync is to execute a command line each time it detects changes
in one of the monitored directories,
or when a directory becomes available
(e. g. insert of a USB-stick). Usually this command line will trigger a FreeFileSync batch job.
RealTimeSync will register to receive change notifications directly from the operating system in order to avoid the overhead of
repeatedly polling for changes.
Each time a file or folder is created/updated/deleted in the monitored directories or their sub directories, RealTimeSync will run the command line.
Example: Real time synchronization using FreeFileSync
Start RealTimeSync.exe located in FreeFileSync's installation directory and
enter the folders you want to monitor. Instead of doing this manually you can import an ffs_batch
file via Menu → File → Open
or simply via drag and drop
RealTimeSync will not only extract all directories relevant for synchronization,
but will also set up the command line to execute the ffs_batch file each time changes are detected.
Now press Start
to begin monitoring.
Example: Automatic synchronization when a USB stick is inserted
Save an ffs_batch configuration in the USB stick's root directory,
and let FreeFileSync run it when the stick is mounted.
But, instead of hard coding the USB drive letter H:\
(which may change occasionally),
refer to the USB stick via its volume name
Configure RealTimeSync as follows:
"Backup" is the volume name of the USB stick in our example.
Whenever directory H:\Data
becomes available, RealTimeSync executes the command line which starts the batch job located
on the stick. RealTimeSync will also trigger each time files are modified in H:\Data
The full path of the last changed file and the action that triggered the
change notification (create, update or delete) are written
to the environment variables %change_path% and %change_action%.
Example: Log names of changed files and directories (Windows)
Show which file or directory has triggered a change. Enter command line:
cmd /c echo %change_action% "%change_path%" & pause
Write a list of all changes to a log file:
cmd /c echo %change_action% "%change_path%" >> %csidl_Desktop%\log.txt
- If multiple changes happen at the same time, only the path of the first file is written to variable %changed_file%.
- While RealTimeSync is executing the command line, monitoring for changed files is deliberately inactive.
The command line usually starts a synchronization task using FreeFileSync which naturally leads to additional file change notifications.
Therefore, the RealTimeSync change detection has to be deactivated to not go into an endless loop.
On the other hand, it is not likely that changes (other than those from FreeFileSync) happen in first place since RealTimeSync runs the command line only after the user-specified idle time has passed.
This makes sure the monitored folders are not in heavy use. In any case, files changed during the execution of FreeFileSync will be synchronized the next time FreeFileSync runs.
RealTimeSync: Run as Service (Windows)
RealTimeSync is designed to run as a background process which does not need further attention.
Depending on your requirements, there are a number of ways to start it automatically.
Generally, the goal is to execute a command line of the form:
<FreeFileSync installation folder>\RealTimeSync.exe <path to *.ffs_real or *.ffs_batch file>
"C:\Program Files\FreeFileSync\RealTimeSync.exe" "D:\Backup Projects.ffs_real"
Example: Run RealTimeSync on Windows login
Create a new shortcut, enter the command line from above as target and place it into the Windows autostart folder.
in the Windows Explorer address bar to find the folder quickly.)
Example: Start RealTimeSync as a Service
RealTimeSync should be monitoring while Windows is running, irrespective of currently logged-in users:
Create a new task in your operating systems's task scheduler and have it execute the command line above when the system starts.
See Schedule Batch Jobs
for an example of how to add a task. Then change
the user which runs the task to SYSTEM
- a special user account always running in the background.
Schedule Batch Jobs
- Create a new batch job via FreeFileSync's main dialog: Menu → File → Save as a batch job...
- By default, FreeFileSync will show a progress dialog during synchronization and
will wait while the summary dialog is shown.
If the progress dialog is not needed, enable checkbox Run minimized and
also set Auto-Close if you want to skip the summary dialog at the end.
Even if the progress dialog is not shown at the beginning, you can make it visible at any
time during synchronization by double-clicking the FreeFileSync icon in the notification area.
- If you don't want error or warning messages to stall synchronization when no user is available to respond,
either check Ignore errors or set Cancel to stop the synchronization at the first error.
- The FreeFileSync batch job can be started by double-clicking on the
ffs_batch file or
it can be set up in your operating system's scheduler:
Be sure to enable Auto-Close and Ignore errors/Cancel if you schedule the ffs_batch file
to run under a different user account. With no one there to close the results dialog manually,
the task would hang indefinitely.
A. Windows Task Scheduler:
- Open the Task Scheduler either via the start menu, or enter taskschd.msc in the run dialog (keyboard shortcut: Windows + R).
- Create a new basic task and follow the wizard.
- Make Program/script point to the location of FreeFileSync.exe and insert the
ffs_batch file into Add arguments.
- Use quotation marks to protect spaces in path names, e.g. "D:\Backup Projects.ffs_batch"
- Program/script always needs to point to an executable file like FreeFileSync.exe even
when the ffs_batch file association is registered.
If an ffs_batch file was entered instead, the task would return with
error code 2147942593 (0x800700C1), "%1 is not a valid Win32 application".
- If you schedule FreeFileSync to run under a different user account, note that the configuration file
GlobalSettings.xml will also be read from a different path,
or in the case of the SYSTEM account from
You can force usage of a particular GlobalSettings.xml file by passing
it as a Command Line parameter.
B. macOS Automator and Calendar:
- Open Launchpad and run Automator.
- Create a new Calendar Alarm.
- Drag and drop the ffs_batch file on the workflow panel.
- Drag and drop action Files & Folders/Open Finder Items and add it to the workflow.
- Go to File → Save... and save the Automator job.
- The Calendar app will start automatically with the Automator job scheduled to the current day. You can now select a different time for synchronization or make it a recurring task.
D. Ubuntu Linux Gnome Scheduled Tasks:
- Install Gnome-schedule if necessary: sudo apt-get install gnome-schedule
- Search the Ubuntu Unity Dash for Scheduled tasks
- Enter the command:
<FreeFileSync installation folder>/FreeFileSync <job name>.ffs_batch
- Select X application since FreeFileSync requires access to GUI
Detect Moved Files
FreeFileSync is able to detect moved files on one side and can quickly apply the same move on the target side during
synchronization instead of a slow copy and delete. To make this work, FreeFileSync requires database files
to compare the current file system state against the time of the last synchronization.
The Two way
variant already creates database files, therefore, detection of moved files is always active.
variant however, does not need the database files to find synchronization directions, so detection of moved files
is not available by default. If you don't mind the creation of the database files, you can enable this feature by
selecting the Detect moved files
- Detection of moved files is not yet possible when synchronizing a folder pair for the first time. Only beginning with the second sync
the database files are available to determine moved files.
- Detection is not supported by all file systems. Most notably, certain file moves on the FAT file system cannot be detected.
Also virtualized file systems, e.g. a mounted WebDAV drive, might not support move detection. In these cases FreeFileSync will automatically fall back to copy and delete.
SFTP and FTP Setup
FreeFileSync supports synchronization with SFTP and FTP natively. Just enter your login information into the dialog shown for cloud folder selection:
In case the (S)FTP server sets file modification times
to the current time
you can do a Compare by File Size
as a workaround.
Another solution is to set up the Two way
variant and have the files with the newer dates
be copied back from the server during the next synchronization.
Configure SFTP for best performance
By default, FreeFileSync creates one connection to the server and uses one SFTP channel, i.e. only a single SFTP command can be sent and received at a time.
Since most of this time is spent waiting due to the high latency of the remote connection, you can speed up reading large folder hierarchies
by increasing both the connection and channel count.
The folder reading time is reduced by a factor of N x M when using N connections with M channels each.
: 10 connections using 2 channels each can yield a 20
times faster folder reading.
- The creation of additional connections and channels takes time. If you are only scanning a small remote folder,
setting up too many connections and channels might actually slow the overall process down.
Creating extra connections is slower than creating extra channels.
- SFTP servers have internal limits on the number of allowed connections and channels.
Generally, servers expect one connection per user, so this number should be kept rather low.
If too many connections and channels are used, the server may decide to stop responding.
- Unlike connections, additional SFTP channels are (currently) only used during folder reading (comparison), but not during synchronization.
Start with low numbers and make tests with different combinations of connections and channels for your
particular SFTP synchronization scenario to see what gives the highest speed.
Note, however, that FreeFileSync reuses existing SFTP connections/channels.
Therefore, you should restart FreeFileSync before measuring SFTP speed.
Variable Drive Letters
USB memory sticks or external hard disks often get different
drive letters assigned when plugged into distinct computers. FreeFileSync
offers two solutions to handle this problem:
Specify a folder path by using the volume name:
Enter the path as [USB-NAME]\folder instead of E:\folder where USB-NAME
is the volume name of the USB stick which is currently mounted in drive E:\.
It is not required to look up and enter the volume name manually. Just select the corresponding entry in the drop down menu.
Option 2: Use a relative directory name:
- Use \folder instead of E:\folder
- Save and copy synchronization settings to the USB stick: E:\Backup.ffs_gui
- Start FreeFileSync by double-clicking on E:\Backup.ffs_gui
The working directory is then automatically set to E:\
by the operating system so that the
relative path \folder
will be resolved as E:\folder
When you need to preserve files that have been deleted or overwritten,
it's often sufficient to select Recycle bin
settings. However, this is only available for local drives and offers
little control on how to store and how long to keep the files.
FreeFileSync therefore has an additional option, Versioning
1. Keep only the most recent versions
In synchronization settings, set deletion handling to Versioning
and naming convention to
. Deleted files will be moved to the specified folder
without any decoration and will replace already existing older
2. Keep multiple versions of old files
- Set deletion handling to Versioning
and naming convention to Time stamp [File]. FreeFileSync will move
deleted files into the provided folder and add a time stamp to each
file name. The structure of the synchronized folders is preserved so
that old versions of a file can be conveniently accessed via a file
Example: Last versions of the file Folder\File.txt inside folder D:\Revisions
D:\Revisions\Folder\File.txt 2020-12-11 111111.txt
D:\Revisions\Folder\File.txt 2020-12-12 122222.txt
D:\Revisions\Folder\File.txt 2020-12-13 133333.txt
- With naming convention Time stamp [Folder] files are moved into a time-stamped subfolder
of the versioning folder while their names remain unchanged.
This makes it easy to manually undo a synchronization by moving the deleted files from the
versioning folder back to their original folders.
Example: Last versions of the file Folder\File.txt inside folder D:\Revisions
3. Save versions at certain intervals
With naming convention Replace
it is possible to refine the granularity of versions to keep by adding Macros
to the versioning folder path. For example, you can save deleted files
on a daily basis by adding the %date%
Last versions of the file Folder\File.txt
inside folder D:\Revisions\%date%
Volume Shadow Copy (Windows only)
FreeFileSync supports copying locked or shared files by creating a Volume Shadow
Copy of the source drive. This feature can be configured via Menu → Tools → Options: Copy locked files
- The volume snapshot created by the Volume Shadow Copy Service is only used for copying files that are actually locked.
- Accessing the Volume Shadow Copy Service requires FreeFileSync to be started with administrator rights.
If you experience problems using the Volume Shadow Copy Service, a renewal of registration might help.
Create and execute a cmd batch file and insert the following lines or enter directly via command line:
cd /d %windir%\system32
Net stop vss
Net stop swprv
regsvr32 /i swprv.dll
regsvr32 /i eventcls.dll