Firecracker
Firecracker is open-source virtualization software for running container and function workloads in lightweight microVMs.
What Firecracker is
Firecracker is open-source virtualization software for running container and function workloads in lightweight microVMs. It uses Linux KVM hardware virtualization to isolate workloads and limits each microVM to five emulated devices, a design intended to reduce its attack surface. The project states that microVMs start in under 125 ms, with less than 5 MiB of memory overhead per VM; a host can create up to 150 microVMs per second and run thousands on one server. A RESTful API configures and starts microVMs, while rate limiters manage network and storage use. Its companion jailer adds Linux user-space security barriers. Firecracker supports Linux hosts and Linux guests with kernel versions 4.14 and above, plus OSv guests, on supported 64-bit Intel, AMD, and Arm CPUs with hardware virtualization. It supports VM snapshots, but not GPU acceleration. Firecracker is free under the Apache 2.0 license. One aarch64 limitation: guest programs using an RTC alarm will not work because the pl031 RTC device does not support interrupts.
Good
- Open source under the Apache 2.0 license
- Supports VM snapshots
- REST API controls configuration and startup
- Built-in controls limit network and storage use
- Supports Linux and OSv guests
Watch out
- No GPU acceleration
- aarch64 RTC alarms do not work
- Requires hardware virtualization support
Who it suits
Firecracker suits teams running container or function workloads that need isolated, lightweight virtual machines and can use Linux hosts. Its REST API, resource controls, and integrations may also suit environments managing microVMs at scale.
Verdict
Firecracker offers lightweight microVMs with stated startup, memory, and host-density characteristics, alongside API controls and a second security layer. Check its hardware and operating-system requirements, and consider the aarch64 RTC alarm limitation if relevant.
Plans and prices
From Firecracker's own pricing page, checked 7 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Firecracker VMM | Free | Open source · Apache 2.0 license |
The facts
Each one read from Firecracker's own pages, with the date it was checked.
What it does
- Control API
- A RESTful API controls the Firecracker process, including microVM configuration and startup.checked 7 Oct 2026
- Density
- Firecracker says a host can create up to 150 microVMs per second and pack thousands onto one server.checked 7 Oct 2026
- GPU acceleration
- Nochecked 20 Sep 2026
- Guest architecture
- bothchecked 20 Sep 2026
- Integrations
- The site lists integrations including containerd, Kata Containers, E2B, Fly.io, Koyeb, Northflank, OpenNebula, Qovery, and microvm.nix.checked 7 Oct 2026
- Isolation
- Firecracker uses Linux KVM hardware virtualization to isolate microVM workloads.checked 7 Oct 2026
- Jailer
- The companion jailer applies Linux user-space security barriers as a second line of defense if the virtualization barrier is compromised.checked 7 Oct 2026
- Minimal design
- Firecracker exposes five emulated devices and says this reduces the attack surface of each microVM.checked 7 Oct 2026
- Notable limitation
- On aarch64, the pl031 RTC device does not support interrupts, so guest programs using an RTC alarm will not work.checked 7 Oct 2026
- Open source and license
- Firecracker is open source and licensed under Apache 2.0.checked 7 Oct 2026
- Operating systems
- Firecracker supports Linux host and guest operating systems with kernel versions 4.14 and above, as well as OSv guests.checked 7 Oct 2026
- Purpose
- Firecracker is open source virtualization technology for running secure, multi-tenant container and function workloads in lightweight microVMs.checked 7 Oct 2026
- Resource controls
- Built-in rate limiters control network and storage resource use, including bandwidth and operations.checked 7 Oct 2026
- Startup and memory
- The site states that microVMs start in under 125 ms and have under 5 MiB of memory overhead per VM.checked 7 Oct 2026
- Support
- The project directs community questions to its Slack workspace and GitHub repository issues.checked 7 Oct 2026
- Supported hardware
- The site lists 64-bit Intel, AMD, and Arm CPUs with hardware virtualization support as generally available for production workloads.checked 7 Oct 2026
- VM snapshots
- Yeschecked 20 Sep 2026
Money
- Free plan
- Yeschecked 20 Sep 2026
Where it runs
- Host platforms
- Linuxchecked 20 Sep 2026
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