---
title: "Files that change while they're being transferred"
url: https://storagestudio.us/wiki/files-that-change-during-a-transfer
category: "Data Transfers"
tags: ["data transfers", "sync", "troubleshooting"]
summary: "A file that is still being written while it's copied — a growing log, an open download — doesn't match by the time the copy ends. Storage Studio finishes everything else, fetches those files once more, and leaves any still changing for the next run."
updated: 2026-10-01T05:33:54.000Z
---

# Files that change while they're being transferred

A file that is still being written while it's copied — a growing log, an open download — doesn't match by the time the copy ends. Storage Studio finishes everything else, fetches those files once more, and leaves any still changing for the next run.

A file that is still being written while Data Transfers copies it — a log file that keeps growing, a download in progress, a document an app is saving — is a different size by the time its copy finishes. Storage Studio notices the mismatch rather than keeping a copy that doesn't match, finishes everything else, and deals with those files separately.

## What happens

For a **Copy**, a **Sync (one-way)** or a **Bidirectional sync** where the only problem was files that were still changing:

1. The transfer is marked **Completed**, and its details say so: *"Everything was copied except 2 files that were still being written"*, followed by their names (up to five, then "…and N more").
2. Straight away, a follow-up **Copy** of just those files starts. It takes them as they are at that moment — for a file that is still being written, that's a snapshot partway through. The follow-up appears in the list as a separate Copy with the same source and destination.
3. If the follow-up finds them changing yet again, it doesn't keep chasing them. It finishes as **Completed** and says the files *"were still changing while being copied, so they were skipped this time"* and *"They'll be copied on the next run."*

The next run — **Sync again**, **Run again** or the next scheduled run — picks them up once they have settled.

```mermaid
%% caption: How a transfer handles files that were still being written
flowchart TD
  A[The transfer finishes] --> B{Did only still-changing files fail?}
  B -->|No| F[The transfer shows Failed with the reasons]
  B -->|Yes| C[Marked Completed and a follow-up Copy starts]
  C --> D{Are those files still changing?}
  D -->|No| E[Copied as they are now]
  D -->|Yes| G[Skipped this time and copied on the next run]
```

*Flowchart — How a transfer handles files that were still being written. Outline:*

- The transfer finishes
  - leads to Did only still-changing files fail?
- Did only still-changing files fail?
  - No: leads to The transfer shows Failed with the reasons
  - Yes: leads to Marked Completed and a follow-up Copy starts
- Marked Completed and a follow-up Copy starts
  - leads to Are those files still changing?
- Are those files still changing?
  - No: leads to Copied as they are now
  - Yes: leads to Skipped this time and copied on the next run

## When it's reported as a failure instead

- **A Move** isn't handled this way. The transfer shows **Failed** with a message that some items *"couldn't be copied because they changed on the source while they were being copied"*, and lists them. The rest of the move went ahead; run it again once those files have settled.
- **A transfer with other problems as well** — a permission error, a full destination — shows **Failed**, and its details list what wasn't copied and why. See [A transfer failed](https://storagestudio.us/wiki/a-transfer-failed).
- **A very large single-file download** stops if the original changes part-way: *"The original changed while it was downloading, so the transfer stopped rather than mixing two versions together."* What arrived is kept; start it again to fetch the new version.

## How to avoid it

- **Close the app that's writing** to the folder before you transfer it, or wait until it has finished saving.
- **Schedule transfers for a quiet time**, such as overnight, when fewer files are open. See [Scheduling a transfer](https://storagestudio.us/wiki/transfer-schedules).
- **Leave out folders that are always busy**, such as an app's live logs or caches. Transfer the folders around them instead.
- **For a folder you're moving to your external drive**, [Data Parking](https://storagestudio.us/wiki/moving-folders-safely) is usually the better tool; see [when an app is holding a folder open](https://storagestudio.us/wiki/when-an-app-holds-a-folder-open) for folders in use.

More answers: https://storagestudio.us/faq

See also: [Sync again and Run again](https://storagestudio.us/wiki/sync-again) · [Copy, Move, Sync or Two-way sync](https://storagestudio.us/wiki/copy-move-sync-or-two-way-sync) · [Data Transfers](https://storagestudio.us/wiki/data-transfers)

## What links here

- [A transfer failed](https://storagestudio.us/wiki/a-transfer-failed)
- [Copy, Move, Sync or Two-way sync](https://storagestudio.us/wiki/copy-move-sync-or-two-way-sync)
- [Two-way sync and the First run box](https://storagestudio.us/wiki/two-way-sync-first-run)
- [When an app is holding a folder open](https://storagestudio.us/wiki/when-an-app-holds-a-folder-open)