The short version
SyncGallery is built around one idea: a sync rule must be understandable before it becomes automatic.
A rule connects a set of files on your Android device with a folder in Google Drive or OneDrive. The rule defines direction, scope, matching behavior, safety thresholds, and what happens when files are changed or removed.
First sync is reviewed. SyncGallery scans both sides, shows the planned operations, and waits for your approval before files move. Later syncs run automatically unless the rule detects risk: a conflict, too many deletes, too many updates, or another threshold you configured.
What a sync rule controls
Think of each rule as an independent agreement between your phone and one cloud destination. Rules do not silently share decisions with each other.
- Direction — upload only, download only, or two-way.
- Scope — individual files you mark, or folders/albums you select.
- Destination — the cloud account and folder used by this rule.
- Existing-file matching — how SyncGallery avoids uploading or downloading files that are already present.
- Safety gates — when a batch is allowed to run automatically and when it must wait for review.
This is why two rules can behave differently even if they use the same cloud account. For example, your personal camera backup may be two-way, while a family member's folder may be download-only and safe to curate locally.
Sync directions
Direction is the most important setting. It decides which side is allowed to change the other side.
Just upload to cloud
Use this when the phone is the source and the cloud folder is mainly a backup or destination. New selected files go from device to cloud. Local changes can update the cloud when the rule allows it.
Cloud-side edits and deletes are not automatically trusted as instructions for your phone. If you want the device to restore cloud files that were deleted or changed remotely, enable the related additional options deliberately.
Just download from Cloud
Use this when the cloud folder is the source and the phone receives a local copy. This is the safest model for family/shared folders because your local cleanup does not write back to someone else's cloud.
Download-only does not have to mean perfect mirroring. You can decide whether locally deleted or locally modified files should be downloaded again later. Leave those re-download options off when you want to curate your own local view.
Two-way sync with cloud
Use this when both sides are yours and both sides should converge. New files on either side appear on the other side. Updates and deletes are evaluated in both directions.
Two-way sync gives the most automation, but it also needs the most safety. It can produce conflicts when the same file changes on both sides before the next scan.
Quick upload
Send files to the cloud whenever you want, without setting up an ongoing sync. Each tap of the rule's icon uploads the files you've selected — no schedule, no automatic re-upload if you change them later.
- Send files on your own schedule — uploads happen only when you tap
- Uploads stay visible in your task history so you can review what was sent
- Choose what happens on name conflicts: rename and keep both, or replace the existing file
Use this when you want to share or back up specific files without committing to a full sync setup.
What belongs to a rule
Scope answers a simple question: which files should this rule care about?
Files I mark
Use this when you want photo-by-photo control. You mark files from the gallery or preview screen, and only those files belong to the rule. They may come from different folders. This is useful for destinations such as Parents, Friends, Best Photos, or Archive.
Folders or albums I select
Use this when an entire folder or album should stay connected to the cloud. With sub-folder monitoring enabled, new files added inside that folder later become part of the same rule automatically.
A rule only manages files inside its scope. If a file is outside the selected folders and was never marked for the rule, SyncGallery does not treat it as missing, deleted, or pending.
Existing files and duplicate search
The most important thing to understand: SyncGallery does not blindly upload everything just because you connect a device folder to a cloud folder. Before creating operations, it first tries to detect files that already exist on both sides and create a stored mapping between them.
- When syncing device folder A with cloud folder B, SyncGallery first checks the files inside that rule pair. By default, it compares the file name with relative path and the file size. If both match, SyncGallery treats the device file and the cloud file as the same item. It does not upload or download another copy; it creates a mapping so future syncs know these two files belong together.
- If “Verify the content when matching” is enabled, SyncGallery also verifies the bytes. It calculates a checksum for the local file and compares it with the cloud-side content information. This is slower, but safer when a name and size match is not enough for your situation.
- If “Search Device for Existing Files (avoid duplicates)” is enabled, SyncGallery searches the device for matching media files outside the selected rule folder. This search always uses a checksum. If the same media file is found anywhere on the device, SyncGallery maps the cloud file to that existing local file instead of downloading a duplicate. If no match is found, the cloud file is downloaded into the device folder selected for this rule. This option applies only to media files.
This section is about avoiding unnecessary copies. Mapping means “these two files are the same item for this rule.” It is not a move, not an upload, and not a download by itself.
Review Pending Operations
The review screen is where SyncGallery shows the exact plan before running a risky or first-time batch.
When review appears
Review appears for the first scan of a new rule, for conflicts, and for batches that exceed your confirmation thresholds. Routine low-risk changes can run automatically after the rule has been established.
What each row means
Each row represents one file and one proposed action: add to cloud, add to device, update on cloud, update on device, delete on cloud, delete on device, or conflict. Where possible, the screen shows both sides so you can compare device and cloud versions.
How the bottom buttons behave
Execute runs the batch using the current action selected on each row. Action applies a chosen action to selected rows. Cancel closes the review without executing the batch. The same files may be evaluated again on the next scan unless you change the rule or ignore selected files.
Nothing in the review list has happened yet. It is a proposed plan, not a log of completed changes.
Confirmation thresholds
Thresholds decide when SyncGallery should stop being automatic and ask you first.
Each rule can use global thresholds or its own custom limits. SyncGallery counts updates and deletes separately for the device side and the cloud side. If one scan would change more than the allowed limit, the whole batch is parked for review instead of running automatically.
Use stricter thresholds for irreplaceable folders. A threshold of 1 means even a single update or delete of that type requires review. Use looser thresholds only for folders where automatic cleanup is expected.
Conflicts
A conflict means SyncGallery cannot safely choose one version without asking you. The most common case is two-way sync where the same file changed on both sides between scans.
Conflict options
Update on device means the cloud version wins. Update on cloud means the device version wins. Keep Both preserves both versions by renaming one copy so they no longer collide.
Keep Both creates a second file so neither version is lost. After that, both files are tracked normally in later scans.
Execute, Ignore, and Cancel
The review screen has several actions because they mean different things. This section explains what decision each one records.
Execute
Execute approves the current plan. SyncGallery runs the selected operations: upload, download, update, or delete, depending on what each row shows.
Ignore
Ignore means “do not sync this file in this rule.” It is not a one-time skip. The file stays excluded until you restore it from the rule's excluded/ignored list.
Cancel
Cancel means “do not run this batch now.” It does not approve anything and does not exclude files. Use it when the plan looks wrong and you want to change the rule, destination, direction, or thresholds before scanning again.
Why SyncGallery asks for file access
Android protects shared storage, so an app cannot freely manage files unless the user grants the required access. SyncGallery needs broad file access for sync rules that can work across folders, preserve folder structures, detect existing files, handle sidecar files, and apply file-level selections.
Without this access, SyncGallery can still be used as a gallery/editor, but cloud sync is unavailable. The permission is used for file operations on your device; your media is not routed through SyncGallery servers.
Cloud transfers are between your Android device and your Google Drive or OneDrive account. SyncGallery does not use a separate cloud storage service of its own for your media.
Recommended setups
Personal backup
Use Just upload to cloud or two-way sync depending on whether the cloud is only a backup or an active working copy. The first sync is always reviewed before anything moves. Set conservative delete thresholds for later automatic runs.
Family/shared folders
Use Just download from Cloud for other people's folders. Keep re-download deleted files off if you want your local cleanup to stay local.
One-tap destinations from preview
Use file-level rules for destinations such as Parents, Friends, Archive, or Best Photos. Each rule can become a visible button on the preview screen.
New phone or restored library
Use first-sync review and consider enabling content verification if you suspect the same files already exist on both sides under different names or folders.
Important behavior to understand
- Notifications let SyncGallery show progress and alerts while sync runs. Without them, background work may still run but you may miss visible progress.
- Battery optimization can delay background sync on some Android devices. For reliable scheduled sync, allow the app to run in the background.
- Sidecar files such as
.xmp,.aae, and.thmmay be kept with the main photo/video when the rule is configured for media workflows. - Rule history matters. Deleting and recreating a rule may remove the stored pairing history, so the next scan may need review again.
- When unsure, review first. If a proposed batch does not look right, cancel it, adjust the rule, and scan again before executing.