SyncDeck

What the app does

SyncDeck copies your important folders to a destination of your choice and keeps them up to date. Create a sync job: choose one destination (a USB drive, a NAS, a Windows share, another computer…), add the folders you want to keep safe, and pick when to sync. The main screen then tells you at a glance whether everything is synced, and when it last succeeded.

SyncDeck uses the same network code as FileDeck, so it can sync to a Pocket NAS (WebDAV) or an SFTP Studio server (SFTP) as well.

Three ways to sync

In Echo and Contribute, changes made in the destination are undone (with a copy kept). In Synchronize, a file changed on both sides is a conflict: choose per job between Keep both (the default: the newer file wins and the other is kept as name (conflict date time).ext), Newer wins, Source wins or Destination wins. A change always wins over a deletion.

Where to sync

Highlights

• Many folders, one destination: each source folder gets its own folder inside the destination, and other files there are never touched
• Schedules: every 1 hour to 7 days, or at a set time on chosen days; missed syncs run as soon as possible
• Wait for the destination: a scheduled sync to a drive that isn't plugged in simply waits and runs as soon as it is connected
• Runs in the background, with the screen off and the app closed, and picks up where it left off after an interruption
• Keep deleted and replaced files for 30 days, and a safety stop when a sync would delete too much
• Preview exactly what a sync would copy, update or delete, before anything changes
• Full history and logs, notifications when a sync finishes, and a reminder when a backup is overdue
• Material 3 design with light and dark themes; adapts to phones, tablets, foldables and Chromebooks

Download

Why SyncDeck isn't on the Google Play Store

Google currently enforces highly demanding and complex requirements to publish new apps (such as mandatory closed testing phases with at least 20 people for 14 days, rigorous identity verification, and heavy administrative overhead). Because we build apps purely for our own enjoyment and want to keep it simple, we prefer to share the app with you directly.

How to Install the App

How to install an APK directly on your phone

1. Tap the download button above and wait for syncdeck.apk to finish downloading.
2. Open the file (via your notification shade or the Files app).
3. Android will ask permission to install unknown apps. Tap Settings and enable "Allow from this source" for your browser or file manager.
4. Go back and tap Install.
5. Open SyncDeck when installation completes.

Installing apps from outside the Play Store is a normal Android feature. You can turn the "unknown sources" permission back off afterwards if you prefer.

How to install an APK via your computer

The cleanest, safest, and most secure way to install an APK file—without modifying your phone's mobile security settings or enabling "Unknown Sources"—is via ADB (Android Debug Bridge) from your computer. This is an official command-line utility supplied by Google for Android developers.

Step 1: Download ADB on your computer (The fastest way)

You do not need to install the massive Android Studio suite. Google provides a lightweight, standalone package called Platform-Tools.

• Windows: Download the official Android SDK Platform-Tools for Windows.
• Mac / Linux: Download the zip package above or install it instantly via your terminal line:
  • Mac (via Homebrew): Run brew install android-platform-tools
  • Linux (Ubuntu/Debian): Run sudo apt install adb

Note: If you downloaded the ZIP file (Windows/Mac), extract it into an easy-to-reach directory, such as C:\platform-tools or your Desktop.

Step 2: Prepare your Android phone

1. Open the Settings app on your phone.
2. Go to About phone (or System > About).
3. Tap Build number 7 times rapidly until a notification pop-up says: "You are now a developer!".
4. Return to the main Settings menu, open the new Developer options panel, and turn on USB debugging.

Step 3: Install the APK file

1. Connect your phone to your computer using a USB cable.
2. Look at your phone's screen: a prompt will ask "Allow USB debugging?". Check the option for “Always allow from this computer” and tap Allow.
3. Move your downloaded APK file directly into the folder where you extracted the platform-tools files.
4. Open Command Prompt (CMD) on Windows or Terminal on Mac/Linux, and change directories to that folder (e.g., on Windows, type: cd C:\platform-tools).
5. Run this command to verify your computer properly detects your device:

   adb devices

   (If you see a serial number followed by the word 'device', you are connected successfully!)
6. Run the installation script command:

   adb install syncdeck.apk

When the terminal returns a Success message, the app is fully installed on your device and ready to launch!

User manual

The app is in U.S. English. It has four tabs: Sync jobs, History, Locations and Settings.

Quick start: back up your important folders

1. On Sync jobs, tap Create a sync job. Choose the mode Echo (exact backup) or Contribute (never delete).
2. Under Destination, tap Change… and choose your external drive (Pick a folder…) or a NAS (Add a network location…, for example SMB with the share Backup). Create a folder such as SyncDeck Backup.
3. Under Folders to sync, tap Add a folder for each folder you want to keep safe. Each one gets its own folder in the destination; you can rename it, switch it off, reorder or remove it.
4. Under When to sync, choose for example every day at 2:00 AM. Keep Wait for the destination on.
5. Tap Save and sync now. The main screen shows, per folder, when it was last synced successfully.

The main screen

• A banner shows "All 6 folders are synced" or "2 of 6 folders need attention", with the oldest successful sync.
• Each job shows its mode, destination, schedule and next run, or a message such as "Waiting for the destination to be connected".
• Each folder shows a status icon (✓ successful, ⚠ finished with errors or stopped, ✗ failed), "Last synced successfully" with the date and time, and the result of the last run.
• While a sync runs: a progress bar, folder n of m, the current file, and Pause, Continue and Stop.
• Buttons: Sync now, Sync all, Preview, Sync anyway (after a safety stop), Duplicate, Turn off and Delete.

Schedules and conditions

Per job, choose Only when I start it, Every 1 h … 7 days, or At a set time on chosen days (every day, weekdays, Mon/Wed/Fri…). A sync missed while the phone was off runs as soon as possible afterwards; a failed or interrupted sync is retried after an hour. In Settings you can limit automatic syncs to Only on Wi-Fi (for network locations), Only while charging and Not when the battery is low. Syncs you start yourself always run.

History

• History › Syncs: every run with its start and finish time (to the second), duration, what started it, its status and totals. Filter on problems or per job.
• Run details: the result per folder and the full log, which you can filter to warnings and errors, copy, save or share. Choose Summary or Every change logging in Settings.
• History › Events: the app's own activity, such as scheduled syncs that became due, waits, interruptions, resumes and restarts.
• History is kept for 7 to 730 days (90 by default). A badge on History shows recent problems.

How your files are protected

• Keep deleted and replaced files (on by default, 30 days): instead of deleting or overwriting, the old file is moved to .SyncDeck/Versions/<date time>/ inside the synced folder.
• Safety stop (50% by default): a folder is not synced when more than that share of its files would be deleted — for example because an empty or the wrong drive is connected. Sync anyway overrides it once.
• A missing folder is never treated as empty. A source folder that can't be found or read is skipped, and nothing below it is deleted on the other side.
• Picking up where it left off. Progress is saved while a sync runs. After an interruption, files already copied are not copied again, and a half-written file is discarded: files are written as a temporary .part file first and only renamed when complete.
• Unplugged drive or dropped network: the folder stops with one clear error; network locations reconnect and retry once.
• Careful comparing. Names that differ only in upper/lower case are matched (USB drives, Windows, NAS), one-hour daylight-saving shifts on FAT/exFAT drives can be ignored, and optional byte-by-byte comparison and read-back verification check every copy.
• Filters per job: wildcard patterns (*.tmp, ~$*, Thumbs.db…), paths, hidden files and a maximum file size.
• A destination inside a source folder (or the other way round) is refused, and links are not followed.

Good to know

• Reliable schedules: allow Run in the background without battery restrictions (Settings shows a button). Without it, Android may delay background syncs. Some brands (Samsung, Xiaomi, Huawei, OnePlus, Oppo) have extra battery settings: set SyncDeck to Unrestricted there.
• Android 15 and newer limit background data syncs to about 6 hours per day. A longer sync pauses and continues later automatically.
• Dates: WebDAV and folders picked with Android's folder picker can't keep the original "date modified". SyncDeck remembers the state instead, so files are not copied again.
• SMB: enter the share name; listing all shares of a server is not supported.
• Very large folders (hundreds of thousands of files) can take a while and use a lot of memory on a phone.
• Notifications: choose to be notified when a sync finishes or only when something went wrong, and get a reminder when a folder hasn't been synced successfully for a number of days (7 by default).

Permissions this app requests

We believe in being transparent about every permission. Here is exactly what the app asks for and why:

Privacy & cost — in plain terms

• No usage data collected. No analytics, telemetry or advertising.
• No personal data requested. No account with us, no sign-up; the only logins are the ones for your own servers.
• No cookies, no tracking. This website sets none either.
• No cloud service. Files go only between the folders and servers you choose. Nothing is ever sent to us.
• No payment, ever. The app is completely free, with no ads and no in-app purchases.

Settings, saved locations, passwords and keys are encrypted with a key in the Android Keystore and kept in the app's private storage. Cloud backup and device transfer of the app's own data are disabled. For the full statement, see Privacy & Disclaimer.

Responsible use & your responsibility

SyncDeck is a hobby and educational project. Syncing can delete files: Echo and Synchronize remove files on the other side when they are deleted at the source. Use Preview before the first sync, keep Keep deleted and replaced files and the safety stop on, and check the main screen and History regularly. One synced copy is not a complete backup strategy: keep more than one backup of files that matter, ideally in different places. Only sync to servers you own or are allowed to use.

The app is provided "as is", for learning and experimentation, without any warranty. Please read the full Privacy Statement & Disclaimer before use — by installing or using the app you accept those terms.

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