--- title: "Backup versions: what's kept and for how long" url: https://storagestudio.us/wiki/backup-versions category: "Backups" tags: ["backups", "versions", "restore"] summary: "Each backup adds a version that stores only what changed. The five most recent are kept, older ones are thinned to one per hour, day, week and month, and every new version is checked once it has been written." updated: 2026-10-01T05:31:45.000Z --- # Backup versions: what's kept and for how long Each backup adds a version that stores only what changed. The five most recent are kept, older ones are thinned to one per hour, day, week and month, and every new version is checked once it has been written. Every backup a set makes becomes a **version**: a point in time you can restore from. A version looks like a full copy of your folders when you browse it, but it only stores what changed since the version before, so keeping many of them takes far less space than many full copies. ## Only what changed is stored The first backup of a set stores everything. After that, each backup stores only files that are new or have changed; anything unchanged is shared with earlier versions instead of being stored again. The same content is stored once even when it turns up in several files or folders of the set. You can see this in **Versions…**: each row shows the date, how many files the version holds, how many were new, and how much new data it added out of the set's total size. See [incremental backup](https://storagestudio.us/wiki/glossary-incremental-backup). ## How long versions are kept Keeping every version for ever would fill any destination, so after each backup Storage Studio thins out older versions. A set keeps: | What | How many | | --- | --- | | The most recent versions | 5 | | One version per hour | for the last 24 hours that had a backup | | One version per day | for the last 30 days that had a backup | | One version per week | for the last 8 weeks that had a backup | | One version per month | for the last 12 months that had a backup | So for recent changes you can go back hour by hour, over the past month day by day, and over the past year month by month. Versions that fall outside all of these are removed from the destination, and the space they used is gradually freed. These rules are the same for every set and aren't changed from the window. ```mermaid %% caption: How versions are thinned out as they get older flowchart LR A[A new backup] --> B[A new version is stored] B --> C[It's checked] C --> D[Older versions are thinned out] D --> E[The 5 most recent are kept] D --> F[One per hour for the last 24 hours with backups] D --> G[One per day for the last 30 days with backups] D --> H[One per week for the last 8 weeks with backups] D --> I[One per month for the last 12 months with backups] ``` *Flowchart — How versions are thinned out as they get older. Outline:* - A new backup - leads to A new version is stored - A new version is stored - leads to It's checked - It's checked - leads to Older versions are thinned out - Older versions are thinned out - leads to The 5 most recent are kept - leads to One per hour for the last 24 hours with backups - leads to One per day for the last 30 days with backups - leads to One per week for the last 8 weeks with backups - leads to One per month for the last 12 months with backups ## Every version is checked After each backup, Storage Studio checks the new version by reading back a sample of what it just stored and making sure it matches. While that happens the set shows **Checking…**, and when the check passes it shows **Protected** and the card says *"Last backup … · verified"*. **Check** on the card runs the same check whenever you like. - If the check **finds a problem**, the set shows **Needs attention**: *"The backup was saved but its safety check didn't pass, so the newest version may be incomplete. Try "Back up now" again."* - If the check **couldn't run at all** — a brief network drop, for example — the backup still counts as saved and the set shows **Protected**, and the next backup is checked as usual. ## What a version doesn't include A version holds the files that could be read at the time. Items in the Trash, temporary files, cache folders and developer package folders are left out, and a file that was locked or in use is skipped rather than failing the whole backup. See [Data Backup](https://storagestudio.us/wiki/data-backup). ## Starting over Versions stay at the destination when you **Remove destination (keeps stored versions)** or switch a set to a new destination. Only **Delete & start fresh…**, or changing a cloud set's passphrase, removes them all — see [Where a backup can go](https://storagestudio.us/wiki/backup-destinations) and [The backup passphrase](https://storagestudio.us/wiki/the-backup-passphrase). - **Can I move my iPhone backups to an external drive on a Mac?** Yes. Finder has no setting for where it keeps iPhone and iPad backups, but Storage Studio can move them to your external drive from What's Using Space: it copies them, checks every file arrived, and only then frees the space on your Mac. Finder keeps backing up to the drive afterwards, so keep… (https://storagestudio.us/faq) - **What is purgeable space on a Mac and how do I clear it?** Purgeable space is storage macOS is holding — old snapshots, cached cloud files, optimised media — that it frees automatically when you need room, which is why "free" space can look smaller than expected. Storage Studio reclaims a lot of it on demand instead of making you wait. (https://storagestudio.us/faq) - **How do I reclaim space from local Time Machine snapshots on a Mac?** macOS keeps point-in-time APFS local snapshots so Time Machine can restore even when your backup drive is away — useful, but they can hold a lot of space. Storage Studio lists every snapshot, shows which are already safely backed up, and reclaims the space you choose in one click. (https://storagestudio.us/faq) See also: [Restoring from a backup](https://storagestudio.us/wiki/restoring-from-a-backup) · [Backup version](https://storagestudio.us/wiki/glossary-backup-version) · [What backup messages mean](https://storagestudio.us/wiki/backup-messages) ## What links here - [Backup version](https://storagestudio.us/wiki/glossary-backup-version) - [Data Backup](https://storagestudio.us/wiki/data-backup) - [Incremental backup](https://storagestudio.us/wiki/glossary-incremental-backup) - [Restoring from a backup](https://storagestudio.us/wiki/restoring-from-a-backup) - [What backup messages mean](https://storagestudio.us/wiki/backup-messages) - [Where a backup can go](https://storagestudio.us/wiki/backup-destinations)