CreateOS Sandbox vs Modal VM Sandboxes
Modal VM Sandboxes fit teams already on Modal whose agents need Docker, systemd or FUSE on a real kernel, with up to 5,000 containers on Team. CreateOS Sandbox fits agents that run past 24 hours or need to pause with memory and fork, at lower published per-hour rates. Both give each sandbox its own kernel: Modal uses Cloud Hypervisor, CreateOS uses Firecracker.
Pricing at a Glance
CreateOS rates verified 17 October 2026. Modal VM Sandboxes pricing as published on 17 October 2026. Rates billed per GB rather than per GiB, or as bundled sizes, are quoted as published rather than converted.
CreateOS Sandbox
Lower compute rate- Compute
- $0.0362 /vCPU-hr
- Memory
- $0.0116 /GiB-hr
Modal VM Sandboxes
- Compute
- $0.0710 /vCPU-hr
- Memory
- $0.0240 /GiB-hr
Modal bills sandbox CPU at $0.00003942 per physical core (2 vCPU) per second and memory at $0.00000667 per GiB per second, with region multipliers of 1.15-1.75x and 3x for non-preemptible, as of 17 October 2026.
Where CreateOS Sandbox Fits Better
What CreateOS Sandbox brings to this matchup, with a plain note on where Modal VM Sandboxes has the edge.
Lower published rates: $0.03616363 per vCPU-hour and $0.01159025 per GiB-hour, against Modal's normalised $0.071 and $0.024.
No session length cap, where a Modal sandbox timeout tops out at 24 hours.
Pause that saves memory and CPU state is in the standard API; Modal's VM memory snapshots are limited to enabled customers.
Fork a paused sandbox into many copies; fork is not published for Modal's VM runtime.
Where Modal VM Sandboxes is strong
It keeps Modal's Sandbox API, images and per-second billing while adding a real kernel, so Docker, systemd and FUSE work inside the sandbox without workarounds, at very high concurrency.
Which to Pick
Pick CreateOS Sandbox if
- Agent sessions must run longer than 24 hours without snapshot and restart.
- You want pause with memory, and fork, on every account.
- Lower per-hour vCPU and memory rates matter more to you than concurrency.
Pick Modal VM Sandboxes if
- Your agents need Docker, systemd, FUSE or eBPF inside the sandbox.
- You need thousands of sandboxes running at once.
- Your code already runs on Modal and you want the same API and images.
Head-to-Head Comparison
Every dimension side by side, checked on 17 October 2026 against each vendor's own docs and pricing pages. "Not published" means we could not find it on the vendor's pages, not that the feature is missing.
| Dimension | CreateOS Sandbox | Modal VM Sandboxes |
|---|---|---|
| Isolation | Firecracker micro-VM with its own guest kernel | Full VM per sandbox on Cloud Hypervisor (gVisor stays Modal's default runtime) |
| Pause and resume | Pause saves disk, memory and CPU state; vCPU stops billing, memory and storage still bill | Filesystem snapshots; VM memory snapshots limited to enabled customers; idle_timeout |
| Fork | Yes, fork a paused sandbox into many independent copies | Not published for VM runtime; new sandboxes can start from filesystem snapshots |
| Outbound network default | Open with no rules; deny-by-default once any host, IP, CIDR or wildcard rule exists, enforced on the host outside the VM | Open by default; block_network, CIDR allowlist, domain allowlist (Beta, TLS/443 by SNI) |
| Inbound access | Closed by default; opt-in public HTTPS URL | Tunnels on *.w.modal.host with connect tokens and an inbound CIDR allowlist |
| Concurrency | 1 / 5 / 20 / 30 by plan; paused sandboxes count toward the cap | Containers per plan: Starter 100, Team 5,000, Enterprise custom |
| Session length | No cap; idle auto-pause 60 s to 24 h, off by default | Default 5 minutes; timeout up to 24 hours |
| Billing | Per second: $0.03616363 per vCPU-hour, $0.01159025 per GiB-hour, storage $0.0001584 per GB-hour; no egress fees, 50 GiB bandwidth budget per sandbox | Per second, normalised to $0.071 per vCPU-hour and $0.024 per GiB-hour; region and non-preemptible multipliers |
| SDKs and interfaces | TypeScript, Go, Python, Rust, C#, Java SDKs (all but TypeScript pre-1.0), CLI, MCP, REST | Python, JavaScript and Go SDKs; Modal CLI |
| GPU | No GPU shapes | No on the VM runtime (GPU Sandboxes need runtime='gvisor') |
Common Questions
What is different about Modal's VM runtime?
It runs each Modal Sandbox as a full Linux VM on Cloud Hypervisor instead of gVisor, so Docker, systemd and FUSE work inside. gVisor stays Modal's default runtime. CreateOS Sandbox always uses a Firecracker micro-VM with its own guest kernel.
Can Modal VM Sandboxes use GPUs?
No. Modal supports GPU Sandboxes only with runtime='gvisor'. CreateOS Sandbox offers no GPU shapes at all, so for GPU work inside a sandbox, Modal's gVisor runtime is the option between these two products.
How long can a Modal VM Sandbox run?
Up to 24 hours, with a 5-minute default, and Modal recommends filesystem snapshots beyond that. CreateOS Sandbox has no lifetime cap: a sandbox runs until you destroy it, pause it, or it auto-pauses after an idle window you set.
Is Docker supported in CreateOS Sandbox the way it is in Modal VM?
Docker 29 is preinstalled in the CreateOS devbox:1 image, but our docs do not describe running containers inside a sandbox. Modal documents Docker inside VM sandboxes, with filesystem snapshots that include /var/lib/docker.
Sources
Checked 17 October 2026.
See CreateOS Sandbox for yourself
Book a demo, or explore the Sandbox and its pricing.