--- title: "Trying a transfer first with Dry run" url: https://storagestudio.us/wiki/dry-run category: "Data Transfers" tags: ["data transfers", "dry run", "sync"] summary: "Tick Dry run (preview only) in New Transfer to rehearse a copy, move or sync. It works out what would be copied, moved or deleted and lists it in the transfer's Log, without changing a single file." updated: 2026-10-01T05:33:50.000Z --- # Trying a transfer first with Dry run Tick Dry run (preview only) in New Transfer to rehearse a copy, move or sync. It works out what would be copied, moved or deleted and lists it in the transfer's Log, without changing a single file. A **dry run** rehearses a transfer without changing anything. Storage Studio looks at the source and the destination, works out what it would copy, move or delete, and writes that into the transfer's **Log** — but no file is copied, moved or removed. It's the safe way to check a **Sync (one-way)** before it deletes anything at the destination. ## Running one 1. In **Data Transfers**, click **New Transfer** and set up the transfer as you normally would. 2. Tick **Dry run (preview only)** at the bottom of the sheet, next to **Start Transfer**. 3. Click **Start Transfer**. The dry run appears in the list like any other transfer and usually finishes much faster than the real thing, because nothing is sent. It still has to look at both sides, so a very large folder can take a little while. ## Reading the result Select the finished dry run and look at the **Log** at the bottom of its details. It lists each file the transfer would have touched, each one noted as skipped because this was a dry run. Look in particular for: - **Files you didn't expect to be included** — check the source path is the folder you meant, not its parent. - **Deletions** — for a **Sync (one-way)** or a **Bidirectional sync**, any file listed as deleted would really be removed on a real run. If something there should be kept, it's in the destination but not the source: copy it into the source first, or choose a different destination folder. - **Nothing at all** — the two sides already match, or the source path is empty or wrong. The **Log** keeps only the most recent lines, so for a big folder it may not show every file — try a dry run on a smaller sub-folder if you need to see everything. Your Mac's files and the destination are exactly as they were before the dry run. ```mermaid %% caption: Using a dry run before the real transfer flowchart TD A[Set up the transfer] --> B[Tick Dry run and start it] B --> C[Read the Log in its details] C --> D{Does the list look right?} D -->|Yes| E[Click Run again or Sync again to do it for real] D -->|No| F[Fix the source or destination and try another dry run] F --> B ``` *Flowchart — Using a dry run before the real transfer. Outline:* - Set up the transfer - leads to Tick Dry run and start it - Tick Dry run and start it - leads to Read the Log in its details - Read the Log in its details - leads to Does the list look right? - Does the list look right? - Yes: leads to Click Run again or Sync again to do it for real - No: leads to Fix the source or destination and try another dry run - Fix the source or destination and try another dry run - leads to Tick Dry run and start it ## Doing it for real When you're happy with the preview, select the dry run and click **Run again** (or **Sync again** for a sync). A repeat run always switches **Dry run** off, so it performs the transfer for real with the same source, destination and settings. See [Sync again and Run again](https://storagestudio.us/wiki/sync-again). ## Things to know - **A scheduled dry run stays a dry run.** If you tick **Dry run** and also pick a **Schedule**, every scheduled run is a rehearsal too, and nothing is ever transferred. Set up the real schedule without **Dry run**. See [Scheduling a transfer](https://storagestudio.us/wiki/transfer-schedules). - **Files can change in between.** A dry run describes the folders at the moment it ran. If files change before the real run, the real run works from what's there then. - **Large downloads aren't split into pieces during a dry run**, because nothing is downloaded. - **The first run of a two-way sync is the exception.** A dry run with **First run for this pair** ticked is a sensible check, but don't use **Sync again** afterwards: a repeat never carries the **First run for this pair** box. Instead, set the transfer up again with that box ticked and **Dry run** off. See [Two-way sync and the First run box](https://storagestudio.us/wiki/two-way-sync-first-run). See [dry run](https://storagestudio.us/wiki/glossary-dry-run) in the glossary. More answers: https://storagestudio.us/faq See also: [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) · [A transfer failed](https://storagestudio.us/wiki/a-transfer-failed) ## What links here - [Copy, Move, Sync or Two-way sync](https://storagestudio.us/wiki/copy-move-sync-or-two-way-sync) - [Copying between two cloud accounts](https://storagestudio.us/wiki/copying-between-two-cloud-accounts) - [Data Transfers](https://storagestudio.us/wiki/data-transfers) - [Dry run](https://storagestudio.us/wiki/glossary-dry-run) - [Google Photos: what's possible and the Takeout route](https://storagestudio.us/wiki/google-photos) - [One-way sync](https://storagestudio.us/wiki/glossary-one-way-sync) - [Scheduling a transfer](https://storagestudio.us/wiki/transfer-schedules) - [Sync again and Run again](https://storagestudio.us/wiki/sync-again) - [Two-way sync and the First run box](https://storagestudio.us/wiki/two-way-sync-first-run) - [iCloud Photos of another Apple ID](https://storagestudio.us/wiki/icloud-photos-of-another-apple-id)