Sync

The Sync screen lets you copy objects from a source to a destination in one direction. There are two modes: Bucket → Bucket (copy between two S3 endpoints) and Local ↔ Bucket (upload local→bucket or download bucket→local — choose a direction).

Note

Sync is additive and one-way. It copies objects that are missing on the destination or differ in size. It does not delete objects that exist only on the destination, and it does not synchronise in both directions simultaneously.

Bucket → Bucket sync

Select the Bucket → Bucket tab on the Sync screen.

Choosing source and destination

Each side has an endpoint picker with three fields:

Field	What to enter
Account	Select the account that owns the bucket
Bucket	Select the bucket within that account
Prefix	Optional folder prefix to scope the sync (for example backups/)

You can sync between different accounts, including accounts on different providers.

S3 Manager prevents you from running a sync if source and destination are identical, or if the destination prefix overlaps the source prefix within the same bucket.

Planning and running

1. Click Preview to compute a sync plan. S3 Manager lists both sides and compares them. The plan shows how many objects need to be copied, how many are already up to date, and the total bytes to transfer. A sample of up to 100 objects to be copied is shown, along with the reason (missing or size).
2. If the plan shows objects to copy, click Run sync to start the transfer. The button is disabled if nothing needs copying.
3. During the run, progress is shown as copied / total objects and bytes transferred. A pulsing indicator also appears in the sidebar — see Global sync status below.
4. Click Cancel at any time to abort. Objects already transferred are not rolled back.

After the sync finishes a summary shows how many objects were copied and how many bytes, plus any per-object failures.

How objects are compared

Two objects with the same relative key are considered up to date if their sizes match. If a destination object has a different size it is overwritten. Metadata and ETag differences are not compared — only size is used.

Same-account vs cross-account

When source and destination are in the same account, S3 Manager uses the S3 server-side copy API so no data transits your machine. When they are in different accounts the object is downloaded from the source and uploaded to the destination through your local connection.

Local ↔ Bucket sync

Select the Local ↔ Bucket tab on the Sync screen.

Direction

Choose a direction before picking locations:

• Upload (local → bucket) — copies files from your local folder to the bucket. Files on the bucket that are not present locally are left alone.
• Download (bucket → local) — copies objects from the bucket to your local folder. Files on disk that are not present in the bucket are left alone.

Choosing locations

• Local folder — click Choose folder… to open a system folder picker and select the directory to use as the local side.
• Bucket — select an account, a bucket, and an optional prefix, the same way as in bucket-to-bucket sync.

Planning and running

The Preview → Run sync workflow is the same as for bucket-to-bucket sync. The comparison logic is identical: objects are matched by relative key, and only size is compared.

During an upload, S3 Manager sets the Content-Type header from the file extension for common types (HTML, CSS, JavaScript, JSON, images, video, PDF, and others). Extensions that are not recognised get no Content-Type.

Downloads are written to the chosen local folder, preserving the object’s relative key as a file path. S3 Manager refuses to write any object whose key would resolve outside the chosen folder (path traversal protection).

Global sync status

While a sync is running, a pulsing green indicator appears in the sidebar with the current progress (Syncing… N/M while copying, or Listing… during the listing phase). Clicking the indicator navigates to the Sync screen so you can monitor or cancel the run.

The indicator disappears when the sync finishes or is cancelled.