---
title: Snapshots
description: Save, restore, and compare your entire game state. Experiment freely — you can always go back.
---

## 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/`, `live/`, and `persist/`

Snapshots don't directly touch `build/`. Instead, they capture the inputs so you can reproduce an exact game state later. When you restore a snapshot, your metadata and directory contents are restored — and the next deploy rebuilds `build/` from that state.

## 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 and the contents of `persist/`, `import/`, and `live/`.

## 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 and directory contents to the state they were in when the snapshot was taken. Your game directory (`build/`) will be rebuilt on the next deploy to match that state.

> Restoring a snapshot doesn't immediately modify `build/`. The next deploy will reproduce the snapshot's state.

## 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 `live/`
- **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 directory file contents — not references to a cache. This means snapshots are self-contained and can be restored even if the shared cache has been cleared.

## Snapshots vs. Backups

| | Snapshot | Full Backup |
|---|---------|------------|
| What it stores | Profile metadata + directory contents | Complete file copies |
| Disk usage | Compact (metadata + file contents) | Same as the instance itself |
| Speed | Near-instant | Slow (copies everything) |
| Restores | Restores metadata + dirs, then redeploy | Copies files back |

Snapshots are lighter than a full backup and faster to create. They capture the inputs, not the entire deployed output — which is all you need, since `build/` can always be reconstructed.
