Development environments / StackBlitz WebContainers alternative

A StackBlitz WebContainers alternative for agents that need a durable cloud computer

WebContainers embeds a Node.js runtime inside your web application and uses the user’s browser and CPU. It powers interactive tutorials, previews and editors. Compare that execution location and application-owned save workflow with a remote Linux computer whose files and installed software survive between agent tasks.

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Reviewed 2026-10-18 · Published by the Sandbox0 team

When StackBlitz WebContainers fits

WebContainers fits interactive Node.js experiences that should execute close to the user inside a browser. It avoids provisioning a remote server for each local preview and supports familiar JavaScript package managers. Keep that local interaction and deployment model central to the decision.

When to consider Sandbox0

Consider Sandbox0 when the agent needs remotely scheduled Linux execution, persistent installed system tools, a complete durable writable RootFS, online growth and supported paused file access. A migration needs its own editor/preview experience and validated runtime compatibility.

Capabilities

StackBlitz WebContainers and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeStackBlitz WebContainersExecution depends on the client browser; these guides do not establish an unattended cloud runtime lifetime guarantee.View evidence ↗Sandbox0ttl and hard_ttl default to 0 (disabled). Configure idle pause and deletion policies for the same persistent sandbox identity; an idle running sandbox still accrues compute charges.Read documentation →
Persistent filesStackBlitz WebContainersAn application can export and reload virtual files; managed durable retention is not established by the in-memory filesystem API.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSStackBlitz WebContainersFilesystem export captures virtual files, not a documented complete persistent Linux operating-system disk.View evidence ↗Sandbox0Persistence extends beyond /workspace to paths such as /usr/local, /etc, and /home. Runtime tmpfs and virtual filesystems are excluded.Read documentation →
Release compute, keep stateStackBlitz WebContainersteardown destroys the runtime and derived handles; the API does not establish a durable remote-machine pause/resume contract.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateStackBlitz WebContainersThe documented filesystem snapshot/export does not establish arbitrary process-memory capture.View evidence ↗Sandbox0Experimental memory checkpoints can preserve compatible process state. Use memory: true on both pause and resume on a compatible deployment. A filesystem checkpoint alone does not preserve running processes.Read documentation →

Online RootFS growth

On growth-enabled images, Sandbox0 automatically expands the writable RootFS as free space runs low, within a configured sparse logical ceiling up to 64 TiB. Agent processes keep running. Growth is enabled in the qualified Cloud region; confirm activation for other regions. Existing images and snapshots retain their captured storage geometry. The ceiling is logical capacity, not preallocated host disk.

WebContainers uses an in-memory virtual filesystem with explicit import/export building blocks. It does not establish automatic online growth of a regional-object-storage-backed Linux RootFS. File export and rehydration should be evaluated separately from continuing a growing machine.

Files while compute is paused

Sandbox0's Files API reads persistent files without resuming compute. Filesystem-only pauses also permit edits; retained-memory pauses are read-only and reject mutations with 409. SSH, SFTP, file watching, and runtime-only mounts require running compute.

See paused file operations →

The filesystem is in memory; saving is an application responsibility

The filesystem guide describes an in-memory virtual filesystem. The API can export a directory as a file tree or binary output and mount a tree or snapshot later. These are useful building blocks for saving projects, but they do not establish a managed durable Linux RootFS or retained live processes. teardown makes the instance, its processes and filesystem handles unusable.

Source 1 ↗Source 2 ↗

Browser requirements affect where your agent can execute

WebContainers relies on browser capabilities including SharedArrayBuffer and cross-origin isolation. Chromium has the strongest documented support; the guide describes limitations in other browsers. This is an execution architecture choice, not a guarantee of an unattended remote machine that stays available after the user leaves the application.

Source 1 ↗Source 2 ↗

API licensing differs from an editor subscription

Commercial for-profit production use requires a WebContainer API license, including customer, prospective-customer and employee use. Prototypes and proofs of concept are exempt from that production-license requirement. The enterprise offer is sales-led; a StackBlitz editor seat price is not a verified commercial embedded-API quote.

Source 1 ↗

Pricing

Compare billing models, then price your workload

CPU allocation, memory, billing minimums, disk, plan fees, and supported workload differ. These meters are not equal-performance machine quotes. Confirm region, resource units, and included allowances before estimating a total.

StackBlitz WebContainers

Pricing reviewed 2026-10-18

Commercial production API license
Contact the WebContainers team for pricing
Rate source ↗
Prototype / proof-of-concept license requirement
Commercial production license not required for this phase
This is a licensing exception, not a promised free cloud VM allowance.
Rate source ↗
Execution resources
User browser and local CPU
Include commercial API licensing and your application/storage services separately.
Rate source ↗
Enterprise options
Custom commercial terms
The vendor lists private installation, private package access, SSO and support options.
Rate source ↗

No public numeric embedded-API rate was established in the reviewed commercial-use page. Do not substitute StackBlitz editor subscriptions, Bolt usage or local CPU cost for that license. Browser-local filesystem export, remote storage and any server-side agent compute are separate responsibilities.

Check current StackBlitz WebContainers pricing ↗

Sandbox0

$0.015/GiB-hour compute (billed by the second at approximately $0.000004167/GiB-second), plus $0.02/GiB-month of retained incremental RootFS and memory checkpoint data. Shared base images and platform recovery retention are excluded; paused sandboxes accrue storage charges only.

Compute / GiB-hour
$0.015
Retained data / GiB-month
$0.02
Paused compute
$0.00

A 4 GiB agent, 100 running hours

$6.00 compute

4 GiB × 100 hours, billed by the second. Keeping 20 GiB of billable incremental data for a full billing month adds $0.40. CPU is derived from memory by the platform; choose a tier that fits your workload.

Understand storage billing →

Before migrating from StackBlitz WebContainers

  1. Inventory Node.js packages, browser headers, virtual files, project save/export storage, editor previews and commercial API obligations.
  2. Port compatible execution to a Sandbox0 template and implement the application’s remote terminal, file and preview connections.
  3. Test package/system compatibility, whole-RootFS retention, online growth, paused file access and user interaction latency, then compare complete licensing and compute/storage costs.

Common questions

Is Sandbox0 a drop-in StackBlitz WebContainers replacement?

Evaluate API compatibility and product scope. These products serve different core workflows, so a change may require a different architecture.

Does keeping files also keep a running agent?

Filesystem state and volatile process state are separate. Sandbox0 requires explicit compatible memory checkpoints to preserve running processes; its default filesystem resume starts fresh processes.

Sources and review scope

The Boat team's Battleships directory is the discovery source. References below describe the product and plan discussed on this page. Check current availability, regional terms and billing units before migrating. Where the cited material does not establish a capability or price, the comparison identifies that uncertainty.

Battleships research record ↗webcontainers.io/guides/working-with-the-file-system ↗webcontainers.io/api ↗webcontainers.io/guides/browser-support ↗webcontainers.io/ ↗webcontainers.io/enterprise ↗Sandbox0 RootFS capacity →

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