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Frequently Asked Questions

Last updated: October 30, 2026.

New to SyncFolder? Start with the User Guide for a complete walkthrough of configuring tasks. This page answers common questions and covers topics that aren't part of the step-by-step guide.

SyncFolder in short

SyncFolder is deliberately kept simple and does not pretend to be a total solution for all synchronization and backup tasks. It is primarily intended for home use.

Key factors:

  • Installation and updates happen through the Microsoft Store, so they are easy and secure.
  • The app copies one or more source folders to a target storage device, or synchronizes folders located on two storage devices for bidirectional synchronization.
  • Four copy methods are available: 1-way sync, 2-way sync, blind copy, and cut/paste. See below for what each one does.
  • Possible storage devices include: internal SSD/HDD, external USB drives, SD/CompactFlash cards, a network share (e.g. a NAS device), a cloud storage folder mounted locally (OneDrive, Dropbox, Google Drive, …), OneDrive accessed directly without a local mount, devices using the Media Transfer Protocol (most Android/iOS phones and tablets), Android devices running the SyncFolder app's Mobile Sync server, and FTP/FTPS/SFTP servers.
  • Backup/synchronization tasks can run manually, on a schedule, at logon, when a file changes, when a matching USB device is plugged in, or from the command line. See Configuring a Task for the full list of triggers.
  • Copying happens incrementally: only folders and files that are new or have changed since the last run are copied. Modified files are copied in full and replace the previous version — no version history is kept by default (see Selective File History to opt in for specific files).
  • The app also supports importing photos and videos from devices connected via USB and/or WiFi — see below.

Important. Since the app lets you assign any folder on your system as source or target location — including things like Documents or AppData — make sure you understand what each copy method actually does before configuring a task. Choosing the wrong target folder for a 1-way sync task, or the wrong A/B folder for a 2-way sync task, can result in important files being deleted.
To reduce the risk of unexpected deletions: the first time a task that can delete files runs, SyncFolder shows a warning instead of deleting anything. On later runs, deletions proceed normally, but if the Recycle Bin is enabled (the default — see Synchronization Actions) the affected files are moved to the task's trash folder first rather than being removed permanently.

Support for Google Drive as a directly-connected cloud storage location (i.e. not mounted as a local folder) is disabled in the app. A recent policy change at Google now requires an external certification company to verify the app's compliance with the Google Drive API, and given the cost involved and our intention to keep offering SyncFolder for free, we've had to disable this option. Google Drive folders that are mounted locally on your computer can still be used like any other folder.

SyncFolder versus other synchronization/backup apps

SyncFolder is aimed at home users, so many features offered by other apps are missing on purpose. User-friendliness and simple configuration are central, so that everyone can back up their important files without trouble.

If you need more advanced capabilities — full backup history, file encryption, binary content validation, and so on — a commercial backup tool is probably a better fit.

Scheduled synchronization/backup

You can configure a task to run automatically daily, weekly, or monthly. SyncFolder checks every 15 minutes in the background whether a task is due — you don't need to have the app open for this. Because of that 15-minute check interval, a task actually runs 0–15 minutes after its configured time, not at the exact minute.

Periodic checking only happens while your computer is active: not while it's locked (screen off) or asleep. As soon as the computer becomes active again — by starting up, unlocking, or waking from sleep — SyncFolder will (within 0–15 minutes) run any tasks that were due during the inactive period.

Automatic retries for certain failures. Normally a scheduled task runs only once when it's due, even if it fails — for example because a file was locked or a disk was full. You then correct the problem and either re-run the task manually or wait for the next schedule.
For a specific set of faults, however, SyncFolder keeps retrying every 15 minutes: the source or destination drive/path isn't specified or available, the backup operation was interrupted, or access to the source or destination isn't allowed.

Background apps must be allowed to run. Scheduled backups run in the Windows background and can be disabled globally in Windows. If a scheduled task doesn't run, check Background Apps in Windows Settings / Privacy and make sure both the global toggle and the SyncFolder toggle are switched on.

1-way sync, 2-way sync, blind copy, and cut/paste

SyncFolder offers four copy methods, each with a different effect on deleted and excluded files. Get this choice right before running a task against a folder with important data in it — see the warning in SyncFolder in short.

  • 1-way sync — makes the destination an exact mirror of the source: new, changed and deleted source files are reflected at the destination. Nothing is ever copied back from the destination.
  • 2-way sync — keeps Location A and Location B identical. Changes on either side (additions, changes, deletions) are propagated to the other side; if the same item was changed on both sides, SyncFolder reports a conflict or resolves it automatically depending on configuration.
  • Blind copy (previously called "direct copy") — copies new and changed files from source to destination, but never removes anything from the destination, even if it was removed from the source.
  • Cut/paste — moves files: copies them to the destination, then deletes them from the source once the copy has succeeded. Files excluded by a filter are never deleted at the source.

The first time a 1-way or 2-way sync task runs — and again after a reset — SyncFolder does not immediately delete anything it would otherwise delete. Instead it shows a notification so you can confirm the deletions (or reconsider the task's configuration) before they happen.

The exact rules for deletions, conflict handling, and the Recycle Bin — including the current defaults — are covered in detail in Synchronization Actions. For how to choose a copy method and configure a task, see Configuring a Task.

File and folder access restrictions

When SyncFolder runs, access to files and folders happens under the access privileges of the currently logged-on, interactive user. This means every source and destination location used in a task must be accessible to the user account that installed the app.

Force task execution when a USB device is inserted

SyncFolder can offer to start a sync/copy task when the USB device assigned as its source or destination is plugged in. Enable this per task on the task settings page; three options are available:

  • Not applicable / do nothing — SyncFolder doesn't react when the removable drive is plugged in.
  • Execute after confirmation — SyncFolder shows a Windows notification with an "execute" button; the task runs when you press it.
  • Execute automatically — SyncFolder shows a notification and runs the task immediately.

If you power off the computer without first ejecting the USB device, SyncFolder will ignore the device's first re-insertion the next time the computer starts. Eject (if possible) and re-insert the device once to resolve this.

Storage locations: drives, network shares, cloud, FTP/SFTP, mobile devices

Setting up each type of storage location — the exact dialogs, fields, and folder pickers involved — is documented in the Selecting a Storage Location guide chapter, which stays in sync with the current version of the app. This section instead collects the troubleshooting notes and background information that aren't covered there.

Network shares (NAS, mapped drives)

See Internal, External or Network Drive for how to select a network share. A few extra things to know:

  • If a network drive doesn't appear under Network in the folder picker and it's a share on another Windows computer, that computer may need its Function Discovery Resource Publication service started. Open services.msc on that computer (Windows key + R, type services.msc, Enter), set the service's startup type to Automatic (Delayed Start), and start it.
  • If the network drive is a NAS device, it may need WS-Discovery enabled — some devices disable this by default for security reasons, which keeps them from appearing under Network in File Explorer. Check your NAS documentation to enable it.
  • If a share requires different credentials than the other shares on the same server, you must identify the server by IP address or a unique name (not a name shared with other connections) when configuring credentials explicitly — see the next point.

Explicit credentials. If SyncFolder can't connect to a network share because Windows didn't auto-connect it (or lost the connection), press the Network button next to that location to enter and test credentials explicitly. Possible test errors:

ErrorMeaning
0The drive is currently connected in Windows — disconnect it first, run the test, then reconnect. If other shares on the same server stay connected, the test still fails; use the server's IP address or a unique DNS/hosts-file name instead.
53The network path was not found.
86 / 1326The user name or password is incorrect.
1219Windows doesn't allow connecting to a share with different credentials than the ones already assigned to it — this also appears if you supply the wrong credentials for a disconnected drive.

WebDAV servers (Nextcloud, ownCloud, …)

See the "Network Drives" section of Internal, External or Network Drive for how to select a WebDAV folder. SyncFolder uses the built-in Windows WebClient service to talk to the server. If the app can't connect, check whether that service has stopped: right-click the Start menu, choose Computer Management, expand Services and Applications ▸ Services, and look for WebClient.

FTP and FTPS servers

See FTP/FTPS Server for setup. Things to know:

  • When using FTPS with a server that supports TLS v1.3, you may run into a handshake error ("Could not authenticate", usually a server-side issue) or a session resumption error ("Unable to build data connection: TLS session of data connection not resumed", seen with some servers such as FileZilla Server). If either occurs, try forcing TLS v1.2 in the server settings; if that doesn't help, fall back to plain FTP (insecure) or SFTP.
  • SyncFolder does not consider file dates when one or both locations is an FTP/FTPS server — FTP servers are inconsistent about reporting the "Modified" timestamp (some don't report it at all, some in UTC, some in local time). Only file size is used to detect changes.
  • Trusted server certificates are saved in trusted_certs.json in the app's local folder. There's no in-app way to manage them — edit the file manually (carefully, to keep valid JSON) to remove one. The file is deleted automatically when you uninstall SyncFolder.

SFTP servers

See SFTP/SSH Server for setup. Common connection errors:

  • Permission denied (publickey) — either no matching public key is configured for your account on the server, or you selected the wrong private key.
  • openssh key type: ssh-rsa is not supported — SyncFolder only supports ssh-ed25519 in OpenSSH format. Either convert an RSA key to PEM format with ssh-keygen -p -f id_rsa -m pem, or generate an ed25519 key with ssh-keygen -t ed25519 -b 4096 — but don't set a passphrase on an ed25519 key (see next point).
  • cipher name aes256-ctr for openssh key file is not supported — a passphrase-protected ed25519 key generated by a recent ssh-keygen uses a cipher SyncFolder's SSH library doesn't support yet. If you need a passphrase, use RSA instead and save it in PEM format: ssh-keygen -b 4096 -m pem.
  • Invalid private key file — the selected file isn't a private key.

Other things to know:

  • Host keys you trust are saved in trusted_hosts.json in the app's local folder — edit it manually to remove one (keep the JSON valid), or just reinstall the app to clear it.
  • Supported private key formats: RSA and DSA in OpenSSL PEM or ssh.com format; ECDSA 256/384/521 in OpenSSL PEM format; ED25519 in OpenSSH format without a passphrase. .ppk files from PuTTYgen are not supported — convert them first.
  • If an SFTP server doesn't correctly preserve the "Modified" date on upload, open Advanced task settings and enable "Don't copy files when only the 'Modified on' date and time has changed" to stop SyncFolder from re-uploading unmodified files on every run.

Mobile devices over USB (MTP)

See Phone, Tablet or Other Mobile Device for setup. Things to know:

  • Unlock the device before executing a task or changing its folder assignment — MTP devices don't always behave correctly while locked, and a locked device can cause a "source/destination folder not available" error.
  • Some MTP devices don't correctly report the "Modified on" date after a file is copied to them. If that causes SyncFolder to keep re-copying unmodified files, enable "ignore 'Modified on' date and time changes" for the task in Advanced task settings, so only file size is used to detect changes.

MTP is less flexible and slower than a regular USB storage device. As alternatives, consider the SyncFolder Photos companion app (copies pictures/videos over WiFi — see below), or running an FTP/FTPS/SFTP server app on the mobile device and connecting to it as an FTP/FTPS or SFTP location instead. SyncFolder has been used successfully with SimpleSSHD and SSH Server / FTP Server by Banana Studio on Android, and FE File Explorer on iOS (which requires copying pictures to a personal folder served by the app first).

SyncFolder Mobile Sync (Android)

See SyncFolder Mobile Sync for setup. This feature synchronizes with an Android device running the SyncFolder app over Wi-Fi, so no USB cable is needed.

OneDrive

See OneDrive for setup — OneDrive is available as a destination only, connected directly through the Microsoft Graph API. A locally mounted OneDrive folder can also be used directly as a regular folder via Internal, External or Network Drive.

Importing photos and videos over USB

SyncFolder can import photo and video files from an external device — a smartphone, camera, or memory card — connected over USB. Both MSC (Mass Storage device Class) and MTP (Media Transfer Protocol) connections are supported. Start an import in one of two ways:

  • Manually — click Import on the start page, or Execute now on the import task in the tasks list, then select the memory card or connected device.
  • Via Windows Autoplay — connect the device by USB and choose "Import photos and videos (SyncFolder)" in the pop-up that appears.

The first time you do this, SyncFolder offers to create a default Import job for photos and videos. This task is added to your task list, can't be removed, and holds the default save location (the Pictures folder by default — you can change it at any time).

The app then scans the device and shows the photos and videos it finds. If you've imported from this device before, only new files are shown by default; click "All" to see everything. Select the items you want and choose "Copy selected" (into the task's configured folder) or "Copy selected to" (into a specific subfolder of it). You can optionally also delete the selected items from the source device after a successful copy.

Importing photos and videos over WiFi

This feature requires the separate SyncFolder Photos companion app, available on the App Store (iOS) and Play Store (Android).

On your computer:

  • Make sure your WiFi network profile allows other devices on the network to reach your computer — this is the default when the network profile is set to Private. Check under Settings ▸ Network & Internet ▸ Status ▸ Modify connection properties ▸ Network profile, or open the network status page directly.
  • Start the SyncFolder app and wait for a connection request from your mobile device.
  • If you don't have an Import job for photos and videos yet, SyncFolder will offer to create one.
  • Accept the device when prompted.

On your mobile device:

  • Start the SyncFolder Photos app, choose the group/folder, and select the items to export — a single tap selects one item, a double tap selects everything between it and a previously selected item.
  • Tap Export (top right), wait for your computer to appear, and select it.
  • Choose the subfolder on the computer to copy into (or create a new one from the mobile app), and wait for the copy to finish.

If your computer doesn't appear on the mobile device: make sure SyncFolder is running and the device has been selected/accepted on the computer, and that both are on the same WiFi network. Some networks block device-to-device communication — this is common on public WiFi hotspots, where WiFi import won't work at all. If automatic discovery fails but the network otherwise allows device-to-device traffic, you can still connect by scanning the QR code on the SyncFolder Settings page from the mobile app.

Importing and exporting the app repository to a new computer

You can copy your entire task configuration to a new computer. On the old computer, open Settings and click Export to save the repository file (apprepository.json) somewhere accessible from the new computer.

On the new computer, install and start SyncFolder, open Settings, click Import, and select the saved file. If the new computer can reach the same source and destination folders as the old one, the tasks should work right away.

The repository file holds all task settings except account credentials for network drives, OneDrive, FTP, and SFTP servers — these are stored in the Windows Credential Manager and must be re-entered on the new installation. SyncFolder's own credentials appear under Web Credentials, named after the task ID with a trailing "-S" (source) or "-D" (destination).

Execute or reset a task from the command line

  • Execute one or more tasks:
    syncfolder.exe --exec taskID[[,] taskID,...] [--reset] [--minimize]
    Find a task's ID near the top of its Configuration or Status view; you can copy it to the clipboard from there. Separate multiple IDs with a comma and/or space. The optional --reset flag resets every listed task (clearing its cache, so the next run behaves as if it had never executed) before running it.
  • Reset one or more tasks without executing them:
    syncfolder.exe --reset taskID[[,] taskID,...] [--minimize]

Add --minimize to automatically minimize the app once it opens, and to close it again once the command finishes executing.

Unlike most Windows commands, syncfolder.exe always exits with code 0 — the command itself only launches the regular app to do the actual work, it doesn't run the task directly.

Task status and progress monitoring

You can follow a task's status and progress in a few places:

  • Start screen — shows a message while a task is running, and an error message (which stays until resolved) if it fails.
  • Tasks list — shows the result of each task's last run.
  • Task status screen — open it via "Show status" on a task for full details, including a Faults section listing every error from the last run.

The app keeps on copying files that are not modified

SyncFolder decides whether to copy a file in this order:

  1. If the source and target file sizes differ, the file is copied.
  2. If the sizes match and neither location is an FTP/FTPS server, SyncFolder compares the "Modified on" date and time; if they differ, the file is copied.
  3. If size and date both match, SyncFolder checks for a difference in the capitalization of the file name; if there is one, the target file is renamed.
  4. If none of the above show a difference, the file is considered unmodified and is not copied.

How the target's attributes (size, date, name) are obtained also matters:

  • The very first run of a task — and any run right after a reset or after the task's location, sync mode, filters, or advanced settings were changed — looks up the real attributes directly from the target device.
  • Every run after that, by default, reads the target's attributes from a cache file instead of the device, which is much faster. You can force the app to always check the real target attributes by enabling the first toggle in the General section of Advanced task settings.

If SyncFolder keeps re-copying files that haven't actually changed:

  • Check the Faults tab on the task's Status page for copy errors — a file that failed to copy is retried on the next run.
  • If the task isn't using the cache described above (e.g. right after a reset or reconfiguration, or with the setting disabled), the target device itself may not be reporting the "Modified on" date correctly. This is a known issue with some USB-connected mobile devices and some FTP servers. Enable "ignore 'Modified on' date and time changes" for the task so only file size is used to detect changes.

SyncFolder and the firewall

Two optional services in SyncFolder need help from the firewall:

  • Usage and crash reporting to Microsoft AppCenter uses outbound TLS on port 443, which is open by default on most systems — though some antivirus software blocks it. You can disable this under Settings ▸ Diagnostics; worth trying if an antivirus keeps reporting a problem related to it.
  • Allowing your phone to connect over WiFi (for photo/video import or Mobile Sync) needs an inbound firewall rule for an ephemeral port in the range 49152–65535, which the app negotiates during device discovery. Enable this under Settings ▸ Companion app.

If both of the above are disabled and none of your tasks use a network storage location (FTP, SFTP, WebDAV, OneDrive, …), SyncFolder doesn't use the internet at all.

Error messages in SyncFolder

Job can't be launched

Usually caused by background execution being disabled in Windows: on Windows 10, enable SyncFolder under Settings ▸ Privacy ▸ Background Apps; on Windows 11, under Settings ▸ Apps ▸ Installed Apps ▸ SyncFolder ▸ Advanced Options. It can also follow a recent Windows update that needs a restart (often shown as a "win32 process can't be launched" error), or a corrupted Store installation — reinstalling the app can help in that case.

Target station is not available

Make sure the configured storage device (USB drive, SSD, …) is plugged in.

Error 0x80070002: The system cannot find the file specified

The file has probably been deleted.

Error 0x80070005: You are not authorized to access the file/folder

Most often SyncFolder isn't allowed full file system access — check Windows Settings ▸ Privacy ▸ File system. It can also mean your Windows user account itself lacks access to certain files or folders; adjust permissions in File Explorer.

Error 0x80070079: The semaphore timeout period has expired

Usually occurs copying very large files to a network drive or USB device: a bad connection, a failing device, or an outdated USB driver. This error can prevent SyncFolder from copying any further files. Check your storage device carefully — if the error persists, the device may be damaged and may need reformatting (ideally to NTFS).

Error 0x8007007b: Invalid syntax in name, …

Occurs when a source file name contains a character not allowed in Windows file names — \, /, :, *, ?, ", <, >, or | — typically coming from a Linux-based source device. Rename the offending files on the source device.

Error 0x80004003: Object reference not set to an instance of an object

The exact cause is currently unclear. Removing and re-inserting the USB device usually resolves it; if not, restart the computer.

System.IndexOutOfRangeException: Index was outside the bounds of the array at CollectFilesAndFoldersFromDestinationFolder

Can occur after changing the Windows region while an existing task is active. Reset the task from its Task Status window to resolve it.

Files not allowed in Windows will continue to be reported until corrected

Reported when SyncFolder finds files with characters in their name that Windows doesn't allow, or duplicate file names in the same directory — both typically coming from Linux storage devices (which allow characters such as CR/LF in names, and where "duplicate" names on a Linux NAS may differ by a character Windows can't distinguish). Invalid-name files are listed with prefix "S" in the Faults tab (invalid characters shown as ?); duplicates are listed with prefix "D". Fix the file names (or remove duplicates) directly on the storage device — e.g. via Telnet/SSH into a Linux NAS — since File Explorer can't show or resolve duplicates itself; third-party duplicate-finder tools can help locate them from Windows.

Antivirus blocking file access

Some antivirus software blocks unknown programs from writing to or deleting files on a drive by default, which can interfere with a background sync/copy task. Check your antivirus documentation for how to allow SyncFolder, or exclude the relevant folders from protection. If asked for the executable's path, it's under C:\Program Files\WindowsApps, with the app's version number in the folder name, e.g. for version 1.2.8: C:\Program Files\WindowsApps\38124JosHuybrighs.SyncFolder_1.2.8.0_x64__t2c8vhzy5m6xy\SyncFolder.Win32Task\SyncFolder.Win32Task.exe. You'll likely need to update this path after SyncFolder is updated.

The app doesn't work as expected

If backups don't run, or stop or get interrupted unexpectedly, enable logging under Settings (toggle Log files). Events are saved to SyncFolderUWP.log and SyncFolderWin32.log — find their location via "Show files in Explorer" on the same Settings page. When a log file grows too large, its content is rolled into a history file (up to 3 are kept, with suffix 1 being the most recent) and a new log file is started.

You can send these files to SyncFolder support via the Support page. If the current log files look unexpectedly small, please also attach one of the history files.

Uninstall the app

As with any Microsoft Store app: open the Windows Start menu, find SyncFolder in the list of apps, right-click it, and choose Uninstall.

What's new, and what's planned next

See the Changelog for everything that has changed across released versions of the Windows and Android apps.