How to run Swift code on Linux in a sandbox

On Runtime, you install Swift once in an image, and every sandbox starts with the compiler ready. Each sandbox is a Firecracker microVM running Ubuntu 24.04.5, the same release that swift.org builds its Ubuntu 24.04 toolchain for. Building an image is free. Swift 6.4.1 was the current release on 26 October 2026. Its Ubuntu 24.04 toolchain download is 1,124,788,555 bytes.

Ways to get Swift

Swift is not in the default image, and Ubuntu 24.04 (noble) has no swiftlang package (Ubuntu's archive, 26 October 2026). Use swift.org's builds:

The toolchain needs these Ubuntu 24.04 packages, as swift.org lists them: binutils git gnupg2 libc6-dev libcurl4-openssl-dev libedit2 libgcc-13-dev libncurses-dev libpython3-dev libsqlite3-0 libstdc++-13-dev libxml2-dev libz3-dev pkg-config tzdata zip unzip zlib1g-dev (Swift on Linux).

Build a Swift image

The recipe installs the dependencies with apt, then unpacks the toolchain with commands. Commands run as root, as they do in swift.org's own Dockerfile. A build machine has 4 GiB of scratch disk by default. You can request up to 32 GiB (image limits), so this recipe asks for 16 GiB.

TypeScriptimport { Runtime } from "withruntime";const deps = [  "binutils",  "git",  "gnupg2",  "libc6-dev",  "libcurl4-openssl-dev",  "libedit2",  "libgcc-13-dev",  "libncurses-dev",  "libpython3-dev",  "libsqlite3-0",  "libstdc++-13-dev",  "libxml2-dev",  "libz3-dev",  "pkg-config",  "tzdata",  "zip",  "unzip",  "zlib1g-dev",];const url =  "https://download.swift.org/swift-6.4.1-release/ubuntu2404/swift-6.4.1-RELEASE/swift-6.4.1-RELEASE-ubuntu24.04.tar.gz";const runtime = new Runtime();await runtime.images.build(  {    name: "swift",    build: { diskMiB: 16384 },    recipe: {      apt: deps,      commands: [        `curl -fsSL ${url} | tar -xz -C / --strip-components=1`,        "chmod -R o+r /usr/lib/swift && swift --version",      ],    },  },  { onLog: (line) => console.log(line.text) },);

Pythonfrom withruntime import Runtimedeps = ["binutils", "git", "gnupg2", "libc6-dev", "libcurl4-openssl-dev", "libedit2",        "libgcc-13-dev", "libncurses-dev", "libpython3-dev", "libsqlite3-0",        "libstdc++-13-dev", "libxml2-dev", "libz3-dev", "pkg-config", "tzdata",        "zip", "unzip", "zlib1g-dev"]url = ("https://download.swift.org/swift-6.4.1-release/ubuntu2404/"       "swift-6.4.1-RELEASE/swift-6.4.1-RELEASE-ubuntu24.04.tar.gz")runtime = Runtime()runtime.images.build(name="swift", build={"disk_mib": 16384}, recipe={    "apt": deps,    "commands": [        f"curl -fsSL {url} | tar -xz -C / --strip-components=1",        "chmod -R o+r /usr/lib/swift && swift --version",    ],}, on_log=lambda line: print(line["text"]))

The toolchain lands in /usr/bin and /usr/lib/swift, as in the official image. swift.org also publishes a .sig signature beside each tarball, which its Dockerfile checks with gpg before unpacking.

Compile and run a program

Start a sandbox from the image, write the source, compile, then run the binary with the network off.

TypeScriptimport { Sandbox } from "withruntime";const source = `struct Point { var x: Double, y: Double }let points = [Point(x: 3, y: 4), Point(x: 6, y: 8)]let lengths = points.map { ($0.x * $0.x + $0.y * $0.y).squareRoot() }print(lengths)`;await using sbx = await Sandbox.create({  image: "swift",  diskMiB: 10240,  network: { internet: false },  timeoutSeconds: 600,  onLeaseEnd: "stop",});await sbx.files.write("/workspace/main.swift", source);const build = await sbx.exec(["swiftc", "-O", "main.swift", "-o", "main"], { timeoutMs: 300_000 });if (build.exitCode !== 0) throw new Error(build.stderr);const run = await sbx.exec(["./main"], { timeoutMs: 10_000 });console.log(run.stdout); // [5.0, 10.0]

Pythonfrom withruntime import Sandboxsource = """struct Point { var x: Double, y: Double }let points = [Point(x: 3, y: 4), Point(x: 6, y: 8)]let lengths = points.map { ($0.x * $0.x + $0.y * $0.y).squareRoot() }print(lengths)"""with Sandbox.create(image="swift", disk_mib=10240, network={"internet": False},                    timeout_seconds=600, on_lease_end="stop") as sbx:    sbx.files.write("/workspace/main.swift", source)    build = sbx.exec(["swiftc", "-O", "main.swift", "-o", "main"], timeout_ms=300_000)    if build.exit_code != 0:        raise SystemExit(build.stderr)    print(sbx.exec(["./main"], timeout_ms=10_000).stdout)

• Disk: a sandbox's diskMiB includes the image, so request more than the default 4 GiB. Without credit, a sandbox has up to 10 GiB (free usage).
• Compile time: set its own timeoutMs on swiftc. The default, 60 seconds, is meant for quick commands.
• Errors: swiftc prints each diagnostic with file, line and column on stderr, so you can return it to a model unchanged.

Test a Swift package

For a package with a Package.swift, resolve dependencies with the network on, then build and test offline:

TypeScriptimport { Sandbox } from "withruntime";await using sbx = await Sandbox.create({ image: "swift", diskMiB: 10240, timeoutSeconds: 1800 });await sbx.files.upload("./MyLibrary", "/workspace/MyLibrary");const opts = { cwd: "/workspace/MyLibrary", timeoutMs: 900_000 };await sbx.exec(["swift", "package", "resolve"], { ...opts, check: true });await sbx.network.set({ internet: false });const tests = await sbx.exec(["swift", "test"], {  ...opts,  onStdout: (t) => process.stdout.write(t),});process.exitCode = tests.exitCode ?? 1;

Linux has no Apple frameworks, such as UIKit or SwiftUI. So this covers server-side and command-line Swift: the standard library, Foundation, and packages that build on Linux.

Without an image

In a plain sandbox, run the same steps with sudo: sudo apt-get update, sudo apt-get install -y for the dependencies, then curl -fsSL <url> | sudo tar -xz -C / --strip-components=1. Or use swiftly, which installs into $HOME/.local/share/swiftly by default. Its --assume-yes option skips the prompts (swiftly reference).

What it costs

Compiling uses CPU. Waiting does not. Runtime bills measured CPU at $0.025 per vCPU-hour, with a floor of a twentieth of a vCPU, and memory at $0.0075 per GiB-hour (pricing). A stored image is charged by its size. An account without credit can store its first three images free. A new account gets 100 free hours of a 1 GB machine in its first 30 days, with no card required.

See also how to run C++ code in a sandbox, a coding agent sandbox and running untrusted LLM code.

Sources

Checked 26 October 2026.

• Install Swift on Linux (Swift 6.4.1, swiftly commands), tarball dependencies for Ubuntu 24.04
• swift-docker Dockerfile for 6.4 on Ubuntu 24.04 (tarball URL and signature check); the tarball's size from its Content-Length header
• swiftly command reference
• swift on Docker Hub (tag 6.4-noble); packages.ubuntu.com, noble: no swiftlang package

Facts on this page were checked on 26 October 2026.