Darwin SDK
How xcross turns an Xcode.xip archive into a host-neutral Darwin Swift SDK, without installing Xcode or macOS.
Compiling for iOS needs Apple’s iOS sysroot and frameworks. xcross gets them from a real Xcode release archive, but it never installs or runs Xcode - it extracts only the files it needs into a private SDK bundle that Swift and LLVM can target directly from Windows or Linux.
Why an Xcode.xip is needed
The iOS sysroot, system frameworks, and Swift compatibility resources are only distributed inside Xcode. xcross does not reimplement or mirror these files - it reads them out of the official archive you download from Apple. There is no way around providing an Xcode.xip.
This step runs once per machine. After xcross sdk install finishes, the resulting SDK bundle is reused for every xcross flutter run and xcross flutter build until you reinstall it.
Downloading Xcode.xip
Get a complete Xcode.xip from xcodereleases.com. Downloading it requires an Apple ID, but not a paid developer account.
NoteThe archive is only used as SDK input. Neither Xcode nor macOS is ever installed or executed - xcross reads the archive’s contents directly.
Installing the SDK
Run xcross sdk install <path-to-Xcode.xip> after xcross setup. Extraction takes a while, so run it somewhere you can leave unattended.
Windows
xcross sdk install C:\Downloads\Xcode.xipLinux
xcross sdk install ~/Downloads/Xcode.xipThe command produces a host-neutral Darwin Swift SDK bundle - an iOS sysroot plus the frameworks Flutter and your plugins link against - named xcross-darwin.artifactbundle and stored under xcross’s config directory:
| Host | Bundle location |
|---|---|
| Windows | %APPDATA%\xcross\swift-sdks\xcross-darwin.artifactbundle |
| Linux | ~/.config/xcross/swift-sdks/xcross-darwin.artifactbundle |
NoteOn Linux the config root follows $XDG_CONFIG_HOME when it is set, falling back to ~/.config.
Re-running xcross sdk install replaces any previously installed SDK, which is the supported way to move to a newer Xcode release.
How extraction works
Xcode.xip is an Apple .xip archive: an xar container wrapping a pbzx-compressed cpio payload. xcross includes its own pure-Dart readers for all three formats, so it can unpack the archive without calling into Xcode, xip, or any macOS-only tool. This is what makes the whole pipeline work on Windows and Linux in the first place.
Licensing
ImportantThe SDK bundle contains Apple’s own SDK and framework files, extracted under the terms you accepted to download Xcode. Do not redistribute the extracted SDK.
Next steps
- Requirements - what else your machine needs before installing the SDK
- Installation - the full setup flow including
xcross setup - Authentication - sign in before your first build
- Architecture - what the SDK is used for on every run