Reference

Component-level reference for darwinOS. Generated documentation, API signatures, and interface specifications. For conceptual background start with the [Architecture overview](/architecture/); for step-by-step walkthroughs see the [Guides](/guides/).

XNU

The kernel — Mach microkernel core, BSD personality, virtual memory, scheduling, IPC.

Browse XNU

IOKit

The driver framework. Families, matching, and the IOService lifecycle.

Browse IOKit

launchd

The service manager. Plist format, activation triggers, XPC integration.

Browse launchd

dyld

The dynamic linker. Mach-O load commands, shared cache, lazy binding, interposing.

Browse dyld

libSystem

The C library umbrella. libc, libpthread, libm, libdispatch, the syscall ABI.

Browse libSystem

Userland

Shells, coreutils, and the CLI tools that ship with a darwinOS install.

Browse userland

Build system

The Makefile layer, toolchain wrappers, image manifest schema, and CI integration.

Browse the build system

Boot

Early boot, EFI loaders, the kernel handoff structure, boot args, and device trees.

Browse boot

Security

Code signing, AMFI, entitlements, sandbox, SIP-equivalent.

Browse security

Filesystems

VFS, the APFS-compatible implementation, HFS+ read-only, mount paths.

Browse filesystems

Looking for something else?

Architecture

The conceptual map — how these components connect.

Read the overview

Glossary

Plain-language definitions for the terms that show up in reference.

Look up a term

Guides

Task-oriented walkthroughs that touch most of the reference.

Browse guides

Contribute

Reference gaps are always worth filling — docs PRs welcome.

Find your lane