Compare microsandbox, Docker and E2B, then select one in Web. This guide is for operators who finished Install Core and Web and need compute for Core-hosted Sessions.
The installer selects no backend. One installation uses one backend. To change it later, reset the deployment first; see Change the sandbox configuration.
Compare the backends
| microsandbox (recommended) | Docker (compatibility) | E2B | |
|---|---|---|---|
| Where sandboxes run | A microVM on your Linux nodes | A container on your Linux nodes | E2B's cloud |
| Nodes to add | Yes | Yes | None |
| You provide | Linux amd64 hosts with systemd and /dev/kvm | Linux amd64 hosts with systemd and rootful Docker Engine | An E2B API key and a template; a public HTTPS URL for Core |
| Isolation | Each sandbox has its own kernel | Containers share the node's kernel | E2B's |
| Idle sandboxes suspend and resume | Yes, with checkpoints | No | Yes, paused in place by E2B |
| Workspace storage | Required, on NFS | Own disk | Own disk |
| Disk limits | Root disk and workspace quota | None | Set by the template |
The field-level differences are in the deployment contract. Host requirements for nodes are in Add and manage nodes.
Docker is a compatibility backend, for trusted workloads and for hosts without /dev/kvm. Its nodes are root-equivalent on their host: add them only on hosts dedicated to sandboxes.
Sandbox nodes run on Linux amd64. When Core runs on macOS or Windows, connect a Linux node or use E2B. Applications can also run self-hosted Sessions on their own machines, with no backend.
Select the backend in Web
- Open Settings → Sandbox and scheduling. The setup wizard asks Where should sandboxes run?: Own machines (microsandbox or Docker) or E2B.
- For Own machines, choose the backend and the sandbox size. Web proposes the default size the Provider declares as Standard, and Advanced settings on the review page holds the exact CPU, memory and disk values. E2B declares no default size, so its review page has no Advanced settings.
- Choose Save configuration. The choice is stored in Core's database.
For Own machines, continue with Add and manage nodes. For microsandbox, first Set up workspace storage. For checkpoint recovery across microsandbox nodes, see Checkpoint recovery across nodes.
Use E2B
E2B needs no nodes, but its sandboxes call Core from E2B's cloud, so Core needs a public HTTPS URL that is not loopback; see Configure the public address.
- Build a template from the Runtime image with Build a template. Its output records the immutable
templateID:build_UUIDvalue. - In the setup wizard, choose E2B. Under Connect E2B, pick a Service or enter a custom Sandbox API URL and Sandbox data-plane domain, enter the API key, then select the Template build from the list Web loads with that key, template first and then its ready build. The key must belong to the team that owns the template.
- Choose Save configuration. Core stores the key encrypted and never returns it.
When you edit a saved E2B configuration, leave the API key blank to keep the saved key. The Template build then stays an editable text field holding the saved templateID:build_UUID. Entering a key makes Web load the list again.
The key and template rules, including key replacement, are in Initial setup and same-provider changes.
Next steps
- microsandbox or Docker: Add and manage nodes.
- Workspaces on NFS: Set up workspace storage.
- Models and keys: continue with Install Core and Web.