Snapshots

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What Are Snapshots?

A snapshot records everything about your instance that affects the build result:

• Profile setup — the metadata (Minecraft version, loader, mod list, settings)
• Directory contents — everything in import/ and persist/, plus the working copy of import content under build/

The working copy is the runtime state of files that came from import/ — configs and other pack files after you've played and changed them. It lives under build/. Snapshots capture that state so you can get those edits back later.

When you restore a snapshot, metadata, import/, persist/, and the working copy under build/ are restored. A later deploy fills in anything else the game still needs from packages and cache.

When to Use Snapshots

• Before a risky change — updating a major mod, switching loaders, tweaking configs
• Before experimenting — trying out a new modpack configuration you might want to undo
• For "save scumming" your mod setup — keep a snapshot of your stable setup and one for experimentation

Creating a Snapshot

1. Select your instance.
2. Open the Snapshots section.
3. Click Create Snapshot.
4. Give it a name and optional description.

Polymerium records the current profile setup, the contents of persist/ and import/, and the import working copy under build/.

Restoring a Snapshot

1. Open the Snapshots section for your instance.
2. Select a snapshot from the list.
3. Click Restore.

Polymerium restores the profile metadata, import/, persist/, and the working copy under build/ to the state they were in when the snapshot was taken.

Comparing Snapshots (Diff)

You can compare two snapshots to see exactly what changed between them:

• Metadata changes — different mods, version, or loader settings
• Added files — new files in persist/, import/, or the working copy under build/
• Removed files — files that existed in the earlier snapshot but not the later one
• Modified files — same path but different contents

This is useful for understanding what a mod update or config change actually did to your instance.

Snapshot Storage

Snapshots store the actual profile setup data and managed directory file contents — not references to a cache. Restoring a snapshot does not require the shared cache for the captured metadata and directories, but a later deploy may still redownload packages, Minecraft assets, libraries, or runtime files that are no longer cached.

Snapshots vs. Backups

Snapshots are lighter than a full backup and faster to create. They capture the inputs and the import working copy — not every log, package link, or unmanaged file under build/ — which is what you need to get back to a known state.