Apptainer vs BuildKit
Apptainer
apptainer.orgBuildKit
github.comSide by side
| Figure | Apptainer | BuildKit |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Windows | Yes | Yes |
| macOS | Yes | Yes |
| Linux | Yes | Yes |
| API | Yes | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 1 |
| Spec score · Container Engines | 8.9 (#1) | 8.9 (#2) |
| Purpose | Apptainer creates and runs containers that package software for portability and reproducibility. | BuildKit is a toolkit for converting source code to build artifacts in an efficient, expressive and repeatable manner. |
| Security model | By default, users retain the same identity inside the container and cannot gain additional host privileges. | BuildKit describes itself as secure by default and usable with untrusted sources. |
| Security reporting | The Technical Steering Committee manages project security, and the policy directs vulnerability reports through private contact with the project. | Security issues should be reported privately to [email protected], and the project currently does not offer a paid security bounty program. |
| Support | Free support resources include Slack, a mailing list, and GitHub, while commercial support and services are offered through CIQ. | The project directs users to the #buildkit channel on Docker Community Slack and to GitHub issues for reporting problems with release binaries. |
Plans
In their own words
Apptainer
Apptainer is a free container platform for creating and running portable, reproducible workloads, with a focus on shared systems and high-performance computing. It packages containers as immutable, single-file Singularity Image Format (SIF) images designed for transport and sharing. By default, users retain the same privileges inside and outside containers. Images can be signed and verified with PGP keys, PEM keys or X.509 certificates, and encrypted containers can run without writing decrypted contents to disk. Apptainer imports containers from OCI registries and aims to support most Docker Hub containers without changes. It can expose host resources such as GPUs, high-speed networks and parallel filesystems, and supports NVIDIA CUDA, AMD ROCm, Intel Gaudi and OCI Container Device Interface accelerators. Running Apptainer requires Linux; Windows and macOS need a Linux virtual machine, with Windows also listed via WSL2. Root access is unnecessary when user namespaces are available. Full functionality requires kernel support for FUSE and unprivileged user namespaces. Community support includes Slack, Google Groups and GitHub, with commercial services through CIQ.
BuildKit
BuildKit is a free toolkit for turning source code into build artifacts. It consists of the buildkitd daemon and buildctl client, and uses LLB, a binary format for describing process dependency graphs. Builds can use Dockerfiles or other LLB-compatible frontends, resolve dependencies concurrently, cache instructions, import and export caches, run nested jobs, and collect unused data automatically. BuildKit supports execution without root privileges and OCI (runc) or containerd workers. Results can be exported as images, local directories, tarballs, Docker tarballs, or OCI tarballs. Cache options include inline, registry, local-directory, and GitHub Actions backends; the README marks GitHub Actions, S3, and Azure Blob options experimental. The daemon provides a gRPC API over a Unix socket by default, with TCP sockets also supported. Binaries are available for Linux, macOS, and Windows. The unofficial Homebrew formula for macOS omits buildkitd; the project gives Lima in a Linux virtual machine as one way to run it. BuildKit is licensed under Apache-2.0.