Browser platforms / Kernel alternative

A Kernel.sh alternative depends on your browser and machine requirements

Kernel is a managed browser platform with a full Linux environment alongside each browser, not merely a remote page-control endpoint. It supports shell processes, files, profiles, managed authentication and app invocations. Compare those browser-centered primitives with a durable general-purpose agent RootFS.

Start buildingCompare capabilities ↓

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

When Kernel fits

Kernel fits browser-heavy agents needing managed browser identity, automation/control APIs, live views, replays, profiles, pools or authentication. Its session-local Linux process APIs can run an agent near Chromium and process downloaded data without another application round trip.

When to consider Sandbox0

Consider Sandbox0 when the core requirement is a complete evolving Linux filesystem with online growth and supported file access while compute stays paused. A migration still needs its own browser lifecycle, profile/authentication, proxy, replay and orchestration choices.

Capabilities

Kernel and Sandbox0: what persists?

Feature comparison with documentation and verification status
Environment and runtime lifetimeKernelThe idle-deletion timeout can be configured up to 72 hours; active clients/control and standby policy are separate.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 filesKernelSaved browser user-data profiles persist across sessions; session-local files and processes are separate.View evidence ↗Sandbox0The writable RootFS survives successful checkpoints, including software, system configuration, dependencies, and user data.Read documentation →
Whole RootFSKernelBrowser-profile retention does not establish an independently durable complete writable Linux RootFS.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 stateKernelSupported browser standby retains state and stops usage billing; GPU browsers are excluded.View evidence ↗Sandbox0Pause compute between tasks; resume on available capacity. Default resume starts fresh processes from the saved filesystem.Read documentation →
Memory and process stateKernelRetaining browser state during standby is not a documented arbitrary VM-memory export/restore contract.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.

Kernel exposes a session-local Linux filesystem and durable browser profiles. The reviewed sources do not establish automatic online expansion of a complete durable RootFS across returning agent tasks.

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 →

A browser profile does not capture the entire Linux computer

Profiles retain Chromium user-data such as cookies, site data, tabs and preferences. With save_changes enabled, deleting or timing out the Kernel browser saves that profile; closing only the automation connection does not. Session processes and local files need their own export because the process guide says VM contents do not survive deletion.

Source 1 ↗Source 2 ↗

Standby stops usage charges while preserving a concurrency slot

Supported browsers enter standby after five seconds without active client/control activity. A connected CDP, WebDriver or Live View client prevents standby, and GPU browsers do not support it. The subsequent idle-deletion timeout defaults to 60 seconds and can reach 72 hours; it is not a universal maximum active runtime. Standby and reserved pools still consume concurrency.

Source 1 ↗Source 2 ↗Source 3 ↗

Browser types and app invocations have separate meters

Headful, headless and GPU browser types have different usage rates and resource profiles. App invocations charge their own active compute and separately created browsers add browser charges. A deployed idle app or browser pool is not billed like an active invocation; plan fees and credits remain separate.

Source 1 ↗Source 2 ↗

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.

Kernel

Pricing reviewed 2026-10-18

Free/Developer platform plan
$0/month plus usage; $5 monthly usage credit
Rate source ↗
Hobbyist platform plan
$30/month plus usage; $10 monthly usage credit
Rate source ↗
Start-Up platform plan
$200/month plus usage; $50 monthly usage credit
Rate source ↗
Default headful browser
$0.0001333336 per active second
Default memory is 8 GB; verify rates for resource overrides.
Rate source ↗
Default headless browser
$0.0000166667 per active second
Default memory is 1 GB; live view and replays are unavailable.
Rate source ↗
GPU-accelerated headful browser
$0.0008000016 per active second
Start-Up/Enterprise feature; standby is not supported.
Rate source ↗
Default app invocation
$0.0000666668 per active second
Based on 4 GB allocation; browsers and external model APIs bill separately.
Rate source ↗

Monthly usage credits do not pay the plan fee. Retain the published second meters and default resource shapes; memory overrides require the effective resource rate. A connected idle automation client can remain billable because it prevents standby. No universal equal-performance Linux VM or whole-machine-storage price is inferred.

Check current Kernel 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 Kernel

  1. Export required session files and profiles, then inventory authentication, browser types, client connections, pools, replays, process APIs and app invocation dependencies.
  2. Port compatible Linux execution/files and supply any required browser, profile, managed-auth, proxy and orchestration services.
  3. Validate browser behavior separately from complete system persistence, online RootFS growth, paused file operations, process requirements and full browser/app/plan charges.

Common questions

Is Sandbox0 a drop-in Kernel 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 ↗kernel.sh/docs/browsers/profiles ↗kernel.sh/docs/browsers/process-execution ↗kernel.sh/docs/browsers/standby ↗kernel.sh/docs/browsers/termination ↗kernel.sh/docs/browsers/concurrency-and-limits ↗kernel.sh/docs/info/pricing ↗Sandbox0 RootFS capacity →

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