FolderSyncr compares two folders, shows a preview of the file operations it plans to perform, and then synchronizes only after you confirm by clicking Synchronize.
This screenshot is captured from the actual WPF application.
Dark mode is also captured from the running application.
Menu rendering is checked in the same smoke run.
Dark-mode dialogs are also checked.
- Choose a left folder.
- Choose a right folder.
- Select the synchronization mode.
- Select the comparison method.
- Click
Compare. - Review the planned actions in the center preview grid.
- Click
Synchronizewhen the preview looks correct.
You can also drag a folder from Explorer onto either path box to set the left or right folder.
Use the gear button to choose TwoWay, mirror, update, or Custom synchronization. Custom lets you choose a separate action for left-only files, right-only files, left-newer files, right-newer files, and files that differ without a clear newer side. The available actions are do nothing, copy left to right, copy right to left, delete left, and delete right. Impossible actions are shown as conflicts during compare.
Use Tools -> Create sample data to create a disposable folder pair under %LOCALAPPDATA%\FolderSyncr\Samples. The sample includes equal files, left-only files, right-only files, newer files on each side, nested folders, and a conflict case.
Use File -> Open configuration to import a FreeFileSync .ffs_gui, .ffs_batch, or .ffs_real file. FolderSyncr preserves all imported folder pairs and local per-pair filters in saved native configurations and compatible FreeFileSync exports. Use the plus button beside the folder path row to edit the preserved folder pairs. The main view shows the first pair, while FolderSyncr.Cli.exe runs every preserved pair with its local filters unless you pass a single -dirpair override. For .ffs_real files, FolderSyncr imports the configured folders but does not start a real-time monitor yet. Unsupported FreeFileSync options are written as import warnings in the app log.
Use Tools -> Open FreeFileSync log to import a FreeFileSync JSON result or log file. JSON results from FreeFileSync batch runs show the synchronization result, start time, duration, errors, warnings, processed item counts, processed byte counts, and referenced log file.
Each synchronization writes a JSON run result to %LOCALAPPDATA%\FolderSyncr\History. The JSON uses FreeFileSync-like fields: syncResult, startTime, totalTimeSec, errors, warnings, totalItems, totalBytes, processedItems, processedBytes, and logFile.
After a successful two-way synchronization, FolderSyncr writes a hidden sync.ffs_db-style JSON inventory to both synchronized roots. The database records the last known left and right fingerprints for each synchronized relative path. FolderSyncr ignores this metadata file during compare and sync previews.
When the database is available, two-way compare uses it to distinguish one-sided changes from conflicts. If both sides changed since the last completed two-way sync, the item is shown as a conflict even when one side has a newer timestamp. If one side deleted an unchanged file, FolderSyncr propagates that deletion to the other side.
FolderSyncr also uses the database to detect moved files. A detected move is shown as a linked copy/delete pair with a move glyph and tooltip in the action column. Synchronization currently applies the move through the existing copy and delete operations.
Use File -> Save or Save as to store the current folder pair, any preserved imported folder pairs, sync mode, custom rules, compare method, filters, external commands, and theme as a .foldersyncr.json file. Use File -> Open configuration to reopen it later, and File -> Reload configuration to discard local changes and load the current file again.
Use File -> Export FreeFileSync configuration to write a compatible .ffs_gui file. The export includes the current or preserved folder pairs, comparison method, standard synchronization mode/direction, and include/exclude filters. FolderSyncr-only settings such as custom rules, theme, recycle-bin deletion, and versioning options stay in the native .foldersyncr.json format.
Use an SFTP or FTP URI in either folder field to compare and synchronize with a remote file server:
sftp://user:password@example.com/backups
sftp://user:p%40ss@example.com:2222/backups
ftp://user:password@example.com/backups
ftp://example.com/public
FolderSyncr supports SFTP and FTP scanning, time/size or content-hash comparison, copying in either direction, and permanent remote delete. Recycle-bin and versioning-folder deletion are local-folder features, so choose permanent delete when a synchronization can delete files on a remote side. FTP without credentials uses anonymous login.
The settings dialog includes a connection/channel count. Values greater than one run file operations in parallel, which is useful for remote transfers. The SFTP compression checkbox makes SSH connections prefer zlib@openssh.com while keeping uncompressed transfer as a fallback.
Enable Use Volume Shadow Copy for locked local files in the settings dialog when a local source contains files held open by another process. If a normal read fails, FolderSyncr creates a temporary Windows Volume Shadow Copy for that volume, reads the file from the snapshot, and removes the snapshot when the read stream closes. Windows may require elevated permissions and an enabled Volume Shadow Copy Service for this to succeed.
Pass a .foldersyncr.json, .ffs_gui, or .ffs_batch file as the first argument to FolderSyncr.exe to open it in the UI at startup. Add -dirpair <left> <right> to override the loaded folder pair.
FolderSyncr.exe Backup.foldersyncr.json -dirpair C:\Source D:\Target
FolderSyncr.exe Backup.foldersyncr.json --minimizedUse FolderSyncr.Cli.exe for true background unattended batch jobs. It compares and synchronizes the saved configuration, writes a FreeFileSync-like JSON result to stdout, optionally writes the same JSON to --json <path>, exits automatically when the run is complete, and returns 0 for success, 1 for warnings, 2 for errors, or 3 for cancellation. Pass multiple configuration files to merge their folder pairs into one in-memory batch run. You can also pass a FreeFileSync GlobalSettings.xml file; FolderSyncr applies supported global settings such as file-time tolerance and verify-copied-files. Add --var NAME=VALUE to define temporary environment variables for this run, --watch to monitor configured folders continuously, --idle <seconds> to set the realtime idle delay, --error-handling show|ignore|cancel to show errors, continue past item errors, or cancel on the first item error, --symbolic-links skip|follow|copy to skip links, follow links as normal files/folders, or copy file links as links, --connections <count> to run file operations in parallel, --sftp-compression to prefer SFTP compression, and --volume-shadow-copy to read locked local files through VSS.
FolderSyncr.Cli.exe Backup.foldersyncr.json --json Backup-result.json
FolderSyncr.Cli.exe Backup.foldersyncr.json --dry-run
FolderSyncr.Cli.exe Backup.ffs_batch -dirpair C:\Source D:\Target
FolderSyncr.Cli.exe BackupA.foldersyncr.json BackupB.ffs_batch --json Merged-result.json
FolderSyncr.Cli.exe Backup.ffs_batch "D:\Different GlobalSettings.xml"
FolderSyncr.Cli.exe Backup.ffs_batch --var ActiveDir=C:\Work
FolderSyncr.Cli.exe Backup.ffs_real --watch --idle 10
FolderSyncr.Cli.exe Backup.foldersyncr.json --error-handling ignore
FolderSyncr.Cli.exe Backup.foldersyncr.json --symbolic-links copyFolderSyncr can run unattended from Task Scheduler with a saved configuration. Create a basic task, choose Start a program, set the program to the full path of FolderSyncr.Cli.exe, and put the configuration path in Add arguments.
"C:\Path\To\Backup.foldersyncr.json"
To override the configured folders for a scheduled run, add -dirpair after the configuration path.
"C:\Path\To\Backup.foldersyncr.json" -dirpair "C:\Source" "D:\Target"
FolderSyncr.Cli is the recommended executable for unattended background jobs. It runs one saved configuration, writes a machine-readable JSON result, returns a process exit code, and exits. For service-style operation, create one or more Task Scheduler tasks with triggers such as At log on, On a schedule, On workstation unlock, or On idle.
Use the WPF app when someone should review the comparison preview. You can start it with a saved configuration and --minimized when you want the session loaded but do not want the window in front immediately.
FolderSyncr.exe Backup.foldersyncr.json --minimized
FolderSyncr.Cli.exe Backup.foldersyncr.json --json "%LOCALAPPDATA%\FolderSyncr\History\latest.json"If a task must use a different folder pair than the saved configuration, add -dirpair <left> <right> to either executable.
Use FolderSyncr.Cli.exe <configuration> --watch to monitor all existing left and right folders from the loaded configuration. When a file or folder is created, changed, renamed, or deleted, FolderSyncr waits until the configured idle delay has passed without another change and then runs the saved synchronization.
The triggered run receives temporary variables named %change_path%, %change_action%, and %changed_file%. change_action is one of create, update, or delete.
Folder paths can use Windows environment variables such as %USERPROFILE%\Documents or %OneDrive%\Backup. FolderSyncr expands them before comparing or synchronizing.
For scheduled scripts, use FolderSyncr.Cli.exe --var NAME=VALUE to create temporary process-level variables for a single run. They are available while the configuration is loaded, while paths are expanded, and to child commands launched during that run, then restored afterward.
FolderSyncr also expands date/time macros: %Date%, %Time%, %TimeStamp%, %Year%, %Month%, %MonthName%, %Day%, %Hour%, %Min%, %Sec%, %WeekDay%, %WeekDayName%, and %Week%.
Windows special-folder macros are supported for common locations, including %csidl_Desktop%, %csidl_Documents%, %csidl_Pictures%, %csidl_Music%, %csidl_Videos%, %csidl_Downloads%, %csidl_Favorites%, %csidl_StartMenu%, %csidl_Programs%, %csidl_Startup%, %csidl_Templates%, and public document/media variants.
For removable drives, use a volume label path such as [Backup-Disk]\folder. FolderSyncr resolves the label to the currently mounted drive and reports a clear error if the drive is not available.
FolderSyncr also accepts Windows volume GUID paths such as \\?\Volume{01234567-89ab-cdef-0123-456789abcdef}\folder. Windows resolves the mounted volume, and FolderSyncr reports a volume-specific error if the GUID path is currently unavailable.
Network folders can use standard UNC paths such as \\server\share\folder or extended UNC paths such as \\?\UNC\server\share\folder. If the share itself is unavailable, FolderSyncr reports the network share name instead of a generic missing-folder message.
TwoWay: copies the newer file to the older or missing side.MirrorLeftToRight: makes the right folder match the left folder, including deletes on the right.MirrorRightToLeft: makes the left folder match the right folder, including deletes on the left.UpdateLeftToRight: copies missing or newer files from left to right without deleting files that exist only on the right.UpdateRightToLeft: copies missing or newer files from right to left without deleting files that exist only on the left.
TimeAndSize: fast comparison using file length and last-write timestamp.ContentHash: slower comparison using SHA-256 hashes.SizeOnly: compares only file length, useful when modification times are unreliable.
The settings dialog also includes a file time tolerance in seconds. The default is 2, which avoids false differences on file systems with coarse timestamp precision.
Use the error handling setting to choose how synchronization reacts to item-level failures: ShowErrors reports and stops, IgnoreErrors marks failed items and continues with the remaining operations, and CancelOnFirstError stops at the first failure.
Use the symbolic-link setting to choose whether links are skipped, followed as their targets, or copied as file links. FolderSyncr skips symbolic links by default.
Enable Ignore one-hour daylight saving time shifts when a file system reports otherwise equal files exactly one hour apart.
Enable Verify copied files by binary compare in the settings dialog when you want FolderSyncr to read copied files back and compare them byte-for-byte before marking the copy operation as done.
Mirror modes can remove files from the target side. Choose the deletion handling mode in the settings dialog:
Permanent: deletes the target-side file.RecycleBin: sends the target-side file to the Windows recycle bin.VersioningFolder: moves the target-side file into the configured versioning folder under a timestamped subfolder.
When using VersioningFolder, choose a versioning mode:
Replace: preserves the original relative path in the versioning folder and replaces an older stored version.TimeStampFolder: stores files below a timestamped subfolder.FileTime: appends the deleted file's timestamp to the file name.
Set a versioning folder before using VersioningFolder; otherwise synchronization stops with an error before deleting the file.
FolderSyncr creates temporary .foldersyncr.lock files in the left and right roots while synchronization is running. If another FolderSyncr process already holds a lock for either side, synchronization stops before changing files.
=>: copy from left to right.<=: copy from right to left.X<: delete from the left side.>X: delete from the right side.==: both sides are equal.!: conflict.
Use the checkbox in the action column to include or exclude an individual planned copy/delete operation before clicking Synchronize.
Double-click a result row to open the existing left-side item, or the right-side item when no left item exists. Right-click a row to open either side, copy the relative path, add that path to the include filter, or add it to the exclude filter.
Use Tools -> External commands to configure row context-menu commands. Store one command per line in the form Name=command line. Press 0 through 9 to run the matching command for the selected comparison rows.
External commands support the FreeFileSync item macros %item_path%, %local_path%, %item_name%, and %parent_path%. Append 2 to use the opposite side, for example %local_path2% or %local_path 2%. Append s to pass all selected items as a space-separated list, for example %local_path s%.
Examples:
Show in Explorer=explorer.exe /select, %local_path% & exit 0
Copy path to clipboard=echo %item_path%| clip
Compare in WinMerge="C:\Program Files\WinMerge\WinMergeU.exe" %local_path% %local_path2%
Filters follow the FreeFileSync wildcard syntax. Separate official FreeFileSync filter items with | or new lines. FolderSyncr also accepts semicolons and commas when loading older FolderSyncr configurations. * matches zero or more characters, ? matches one character, and ?* requires at least one character. Matching is case-insensitive.
By default, a filter item can match either files or folders. When a rule matches a folder, all descendants of that folder are matched too. A trailing : marks a file-only filter, while a trailing slash marks a folder-only filter. Start a path with \ or / to anchor it to the folder-pair root.
Imported FreeFileSync configurations can carry local filters on each folder pair. FolderSyncr preserves those filters for native saves, exports, and CLI batch runs. The folder-pair editor can edit each pair's include and exclude filters; the filter dialog edits the visible first pair.
Include only text and markdown files:
*.txt | *.md
Exclude build and repository folders:
bin\ | obj\ | .git\
Match only items below subfolders, not files directly in the folder-pair root:
*\
Use the funnel button in the top command bar to edit include and exclude filters.
- Use the gear button to edit synchronization mode and comparison method.
- Use the
Viewmenu to reopen the Configuration and Overview panes after closing them. - Use the bottom overview button to reopen the Overview pane, and select an Overview row to show only that folder group in the file grid.
- Use the bottom
*,==,=>,<=,X<,>X, and!buttons to filter the file grid by all items, equal items, left-to-right copies, right-to-left copies, left deletes, right deletes, or conflicts.
Use the Dark mode / Light mode button in the top command bar to switch themes.
Always run Compare before Synchronize. Mirror modes can delete files from the target side, so test with disposable folders before using FolderSyncr on important data.