# What is a sandbox snapshot?

A sandbox snapshot is a saved copy of a sandbox's machine that you can start new sandboxes from later, as many times as you like.

**On Runtime a snapshot keeps the whole machine, is copied off its server as
soon as it is taken, and costs $0.08 per decimal GB per 30-day month on the
bytes it alone stores** (rate in force since 23 September 2026). Blocks two of
your snapshots share count once ([pricing](/docs/pricing#snapshots-images-and-volumes)).

## Why AI agents use snapshots

Setting a machine up is often the slowest part of an agent's task: cloning a
repository, installing its dependencies, building it, starting a database. A
snapshot lets you do that once. Every later task starts from the prepared
machine instead of repeating the setup, which suits evaluation runs,
reinforcement learning environments and per-user workspaces that should all
begin from the same known state.

## Snapshot, pause, fork and image

| Mechanism                                   | What it keeps                                  | What you do with it                             |
| ------------------------------------------- | ---------------------------------------------- | ----------------------------------------------- |
| [Pause](/how-to/pause-and-resume-a-sandbox) | Files, memory and processes of one sandbox     | Wake the same sandbox later, on the same host   |
| Snapshot                                    | A saved copy of a sandbox                      | Start new sandboxes from it, any time later     |
| [Fork](/glossary/sandbox-fork)              | Files, memory and running processes            | Running copies now, 1 to 10 at a time           |
| [Custom image](/docs/images)                | A filesystem built from a recipe or Dockerfile | Start every sandbox with dependencies installed |

## Runtime's snapshots in facts

| Fact           | Value                                                                        |
| -------------- | ---------------------------------------------------------------------------- |
| Price          | $0.08 per decimal GB per 30-day month, 119 microdollars per GiB-hour         |
| Charged on     | The bytes the snapshot alone stores                                          |
| Retention      | 7 days by default; 1 to 365 days with `retentionDays`                        |
| Durability     | Copied off its server, encrypted, as soon as it is ready, at no extra charge |
| Taking one     | Pauses a running sandbox for about a second when fresh, then wakes it        |
| Where it lives | On its source's server, where sandboxes started from it run                  |
| Volumes        | A sandbox with volumes cannot be snapshotted                                 |

A snapshot's rate is fixed when you make it and never changes. If its server is
lost, the snapshot is restored from its copy onto another
([storage and backups](/docs/storage#snapshots-survive-their-server)).

## Take one and start from it

```ts check
import { Runtime, Sandbox } from "withruntime";

const runtime = new Runtime();
await using base = await Sandbox.create();
await base.exec("pip install --quiet requests");

const snapshot = await base.snapshot({ name: "with-requests", retentionDays: 7 });
await using later = await runtime.sandboxes.create({ snapshot: snapshot.id });
await runtime.snapshots.delete(snapshot.id);
```

```python check
from withruntime import Runtime

runtime = Runtime()
with runtime.sandboxes.create() as base:
    base.exec("pip install --quiet requests")
    snapshot = base.snapshot(name="with-requests", retention_days=7)
    with runtime.sandboxes.create(snapshot=snapshot["id"]):
        pass
    runtime.snapshots.delete(snapshot["id"])
```

From the CLI, `runtime sandbox snapshot <id> --name ready` takes one and
`runtime sandbox create --snapshot <snapshot>` starts from it
([CLI](/docs/cli#images-volumes-and-snapshots)). The full reference is in
[snapshots and forks](/docs/javascript#snapshots-and-forks).

## Related

- [What is a sandbox fork?](/glossary/sandbox-fork)
- [What is a cold start?](/glossary/cold-start)
- [How to pause and resume a sandbox](/how-to/pause-and-resume-a-sandbox)
- [Agent evals and SWE-bench](/use-cases/agent-evals-and-swe-bench)
- [RL environments](/use-cases/rl-environments)

Facts on this page were checked on 25 September 2026.