# Modal vs Northflank: sandbox pricing, isolation and limits Modal isolates with gVisor and bills requested CPU; Northflank runs Kata or gVisor microVMs and bills allocated CPU at a lower rate. **Runtime runs the same job for 84% less than Modal and 42% less than Northflank.** 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $3.97 on Modal, $1.11 on Northflank and $0.64 on Runtime, for an agent that mostly waits on a model. Runtime bills the CPU the code uses rather than the CPUs it holds, and creates a sandbox in one call with no App or service. Rates checked 23 September 2026. ## At a glance | | Modal Sandboxes | Northflank | Runtime | | --------------- | --------------------------------------------------------- | ------------------------------------------------------ | -------------------------------------------------------- | | Isolation | gVisor, a user-space kernel that intercepts system calls | A microVM per workload, with Kata Containers or gVisor | Firecracker microVM, own kernel | | CPU | $0.1419 per physical core-hour (2 vCPUs), request or use | $0.01667 per allocated vCPU-hour | $0.025 per vCPU-hour of measured CPU, with a small floor | | Memory | $0.0240 per GiB-hour, request or use | $0.00833 per GB-hour | $0.0075 per reserved GiB-hour | | Plan fee | Starter $0 with $30 a month of compute; Team $250 a month | None published for compute | None; prepaid credit from $10 | | Free start | $30 of compute a month on Starter | 2 free services and 1 free database | 50 sandbox hours, no card | | Session length | Up to 24 hours; snapshots carry state beyond that | No forced time limit, seconds to weeks | Leases of up to an hour, extended as often as needed | | What you create | A Sandbox, attached to a Modal App | A service with a deployment plan | A sandbox, in one call | ## Why is Northflank so much cheaper than Modal? Both bill what a sandbox holds for as long as it runs, so the rates decide, and Northflank's are lower on both meters. A vCPU costs $0.071 an hour on Modal (half of a $0.1419 physical core) against $0.01667 on Northflank, a quarter as much. Memory costs $0.0240 per GiB-hour on Modal against $0.00833 per GB-hour on Northflank. Put together, a 2 vCPU, 4 GiB sandbox costs about $0.24 an hour on Modal and about $0.067 on Northflank, so Modal is about 3.6 times the price whether the code is busy or waiting. Runtime charges for measured CPU instead. For an agent that waits on a model, that makes it cheaper than both. ## Which one has GPUs, longer sessions or your own cloud? - **GPUs:** both. Modal sandboxes can use GPUs. Northflank rents H100s and other GPUs, at $2.74 an hour all-in for an H100, and uses gVisor for GPU workloads. - **Session length:** a Modal sandbox runs for up to 24 hours, and a snapshot carries its state into a new one. Northflank states no forced time limit. - **Your own cloud:** Northflank runs sandboxes in its own regions or inside your VPC on AWS, GCP, Azure or Oracle. A Runtime lease lasts up to an hour and can be extended as often as needed, or a paid sandbox can be made `persistent`. A sandbox that goes quiet can pause itself and wake on the next request, with its memory and processes intact: ```ts check import { Sandbox } from "withruntime"; const dev = await Sandbox.getOrCreate("agent-worker", { idlePauseSeconds: 600 }); console.log((await dev.exec("uptime", { check: true })).stdout); // Ten quiet minutes later it pauses; the next exec wakes it where it left off. ``` ## Cost for the same job 1,000 runs of a 2 vCPU sandbox (one physical core on Modal) with 4 GiB, or 4 GB on Northflank. Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that mostly waits for a model. ``` Modal CPU 1,000 × 60 s × 1 core × $0.00003942 = $2.37 Memory 1,000 × 60 s × 4 × $0.00000667 = $1.60 Total $3.97 Northflank CPU 1,000 × 60 s / 3,600 × 2 × $0.01667 = $0.556 Memory 1,000 × 60 s / 3,600 × 4 × $0.00833 = $0.555 Total $1.11 Runtime CPU 1,000 × 20 s / 3,600 × $0.025 = $0.14 Memory 1,000 × 60 s / 3,600 × 4 × $0.0075 = $0.50 Total $0.64 ``` At 100,000 runs a month that is $396.60 on Modal, $111.10 on Northflank and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime against $3.97 on Modal and $1.11 on Northflank, so Northflank is the cheapest of the three for work that keeps every CPU busy. Runtime costs less than Northflank until a run keeps its CPUs busy for about 88 of its 120 CPU-seconds. Plan fees, storage, network and free allowances are left out. ## Which one to pick - **Pick Modal** if you already run Modal functions, web endpoints and scheduled jobs and want sandboxes beside them in the same SDK, with GPUs. - **Pick Northflank** for CPU-bound work that keeps every core busy, sandboxes in your own cloud account, or sessions that run for weeks. - **Pick Runtime** for agents that spend most of their time waiting: measured CPU makes it 42% cheaper than Northflank and 84% cheaper than Modal, and pause keeps memory and running processes for 1 to 365 days. ## Switch from either one From Modal, the calls map one to one: `modal.Sandbox.create(app=...)` becomes `Sandbox.create()`, `sb.exec(*args)` becomes `exec`, `Sandbox.from_name` becomes `Sandbox.getOrCreate(name)` and `idle_timeout` becomes `idlePauseSeconds`. From Northflank, a sandbox is no longer a service: replace the service and its deployment plan with `Sandbox.create()`, and map the commands, files and teardown with the table in [migration](/docs/migrate#map-the-calls). Or give your coding agent the one instruction in [migration](/docs/migrate): it switches the project on a branch, tests it on the free trial and reports the monthly saving. From Modal, `npx withruntime switch --from modal` before your first top-up matches that top-up with credit, up to $100. The full side-by-sides are [Runtime vs Modal](/docs/modal-sandbox-alternative) and [Runtime vs Northflank](/docs/northflank-alternative); for the isolation question, see [Firecracker vs gVisor](/compare/firecracker-vs-gvisor). ## Sources Northflank's sandboxes page rechecked 25 September 2026; the rest checked 23 September 2026. - [Modal pricing](https://modal.com/pricing), [Modal resources and billing](https://modal.com/docs/guide/resources), [Modal Sandboxes](https://modal.com/docs/guide/sandbox), [Modal security](https://modal.com/docs/guide/security) - [Northflank pricing](https://northflank.com/pricing), [Northflank sandboxes](https://northflank.com/product/sandboxes), [Sandboxes on Northflank](https://northflank.com/docs/v1/application/sandboxes/sandboxes-on-northflank) - Runtime [pricing](/docs/pricing) Facts on this page were checked on 25 September 2026.