Homebrew (brew) In-Depth Reference

Comprehensive reference for Homebrew — the missing package manager for macOS (and Linux). Covers the full CLI surface, the formula and cask DSLs, the installation pipeline, taps and bottles, services, bundle, environment variables, and developer tooling.

Data Flow

brew install <formula>
  → Formulary loads formula (API JSON or tap .rb file)
    → FormulaInstaller
      → Fetch phase (bottle download or source download)
        → Install phase (pour bottle OR build from source via superenv)
          → Clean phase (remove build-only files)
            → Finish phase (link keg into prefix, run post-install)
              → Tab written (INSTALL_RECEIPT.json)

brew install --cask <cask>
  → CaskLoader loads cask (.rb from tap or API)
    → Cask::Installer
      → Download (curl)
        → Verify (sha256)
          → Extract container (dmg/zip/tar)
            → Stage in Caskroom
              → Preflight → install artifacts → Postflight

Sub-Resources

Load the reference that matches your task. When in doubt, load multiple references.

Keywords	Reference
install, uninstall, reinstall, upgrade, update, search, info, list, ls, fetch, formula, cask, formulae, casks, --formula, --cask, --build-from-source, --force-bottle, --HEAD, --dry-run, --ignore-dependencies, --only-dependencies, --cc, --keep-tmp, --overwrite, --adopt, --zap, --require-sha, --binaries, brew command, brew commands, brew help, brew home, --version, --cache, --cellar, --caskroom, --prefix, --repository, --env, shellenv, brew which-formula, brew source, brew docs, global options, --debug, --verbose, --quiet	references/commands.md
formula, Formula class, formula DSL, def install, depends_on, resource, url, sha256, version, head, license, desc, homepage, bottle block, keg_only, conflicts_with, uses_from_macos, option, deprecated_option, patch, livecheck, service do, caveats, post_install, test do, revision, version_scheme, fails_with, std_cmake_args, std_configure_args, std_go_args, std_cargo_args, std_meson_args, std_pip_args, ENV, superenv, on_macos, on_linux, on_arm, on_intel, on_system, prefix, bin, lib, include, share, libexec, opt_prefix, FormulaInstaller, Formulary, formula loading, path loading, API loading, tap loading	references/formula.md
cask, Cask, cask DSL, cask stanza, version, sha256, url, app, pkg, installer, binary, manpage, font, zap, uninstall, caveats, auto_updates, conflicts_with, depends_on, container, livecheck, no_autobump, deprecate, disable, language, rename, suite, stage_only, artifact, preflight, postflight, preflight_steps, postflight_steps, generate_completions_from_executable, Cask::DSL, Cask::Installer, CaskLoader, Caskroom, --appdir, --fontdir, --language, --require-sha, cask vs formula	references/cask.md
tap, untap, tap-info, tap-new, homebrew/core, homebrew/cask, CoreTap, CoreCaskTap, third-party tap, homebrew- prefix, tap directory structure, Formula/, Casks/, cmd/, Aliases/, API mode, git clone mode, brew tap --repair, --custom-remote, tap trust, brew trust, brew untrust, HOMEBREW_NO_INSTALL_FROM_API, formula resolution order, fully qualified name	references/taps.md
bottle, BottleSpecification, bottle block, bottle tag, pour, relocate, relocation, --build-bottle, brew bottle, --skip-relocation, --force-core-tap, --no-rebuild, --keep-old, --json, --merge, --write, --no-commit, --root-url, ghcr.io, GitHub Container Registry, HOMEBREW_BOTTLE_DOMAIN, bottle naming convention, brew unbottled, --tag, --dependents	references/bottle.md
services, brew services, service do, service block, run, run_type, interval, cron, keep_alive, launch_only_once, require_root, environment_variables, working_dir, log_path, error_log_path, restart_delay, sockets, nice, process_type, throttle_interval, macos_legacy_timers, name, launchctl, launchd, systemctl, systemd, LaunchAgents, LaunchDaemons, start, stop, restart, run, kill, cleanup, --all, --file, --json, --keep, --no-wait, --max-wait, sudo, std_service_path_env	references/services.md
bundle, Brewfile, brew bundle, brew bundle install, brew bundle dump, brew bundle cleanup, brew bundle check, brew bundle exec, brew bundle sh, brew bundle list, brew bundle add, brew bundle remove, brew bundle edit, brew bundle env, brew bundle upgrade, tap entry, brew entry, cask entry, mas entry, vscode entry, go entry, cargo entry, uv entry, flatpak entry, winget entry, krew entry, npm entry, whalebrew entry, cask_args, restart_service, start_service, link, conflicts_with, postinstall, version_file, greedy, trusted, HOMEBREW_BUNDLE_FILE, HOMEBREW_BUNDLE_JOBS	references/bundle.md
environment variable, HOMEBREW_PREFIX, HOMEBREW_CELLAR, HOMEBREW_REPOSITORY, HOMEBREW_CACHE, HOMEBREW_TEMP, HOMEBREW_NO_INSTALL_FROM_API, HOMEBREW_NO_AUTO_UPDATE, HOMEBREW_AUTO_UPDATE_SECS, HOMEBREW_API_DOMAIN, HOMEBREW_BOTTLE_DOMAIN, HOMEBREW_ARTIFACT_DOMAIN, HOMEBREW_CASK_OPTS, HOMEBREW_NO_ANALYTICS, HOMEBREW_DEBUG, HOMEBREW_DEVELOPER, HOMEBREW_COLOR, HOMEBREW_EDITOR, HOMEBREW_BROWSER, HOMEBREW_GITHUB_API_TOKEN, HOMEBREW_FORCE_BREWED_CURL, HOMEBREW_FORCE_BREWED_GIT, HOMEBREW_SORBET_RUNTIME, HOMEBREW_NO_INSECURE_REDIRECT, HOMEBREW_CLEANUP_MAX_AGE_DAYS, HOMEBREW_DOWNLOAD_CONCURRENCY, HOMEBREW_FORBIDDEN_TAPS, HOMEBREW_FORBIDDEN_FORMULAE, HOMEBREW_ALLOWED_TAPS, brew.env, brew config, brew doctor, configuration	references/environment.md
cleanup, autoremove, prune, brew cleanup, --prune, --scrub, --prune-prefix, brew autoremove, --dry-run, brew doctor, --list-checks, --audit-debug, brew missing, brew migrate, brew pin, brew unpin, brew outdated, --json, --greedy, --fetch-HEAD, brew leaves, --installed-on-request, --installed-as-dependency, brew tab, brew linkage, --test, --reverse, --cached, INSTALL_RECEIPT, tab metadata	references/maintenance.md
deps, uses, brew deps, brew uses, --topological, --direct, --tree, --graph, --dot, --annotate, --union, --include-build, --include-optional, --include-test, --include-implicit, --skip-recommended, --installed, --missing, --for-each, --HEAD, --os, --arch, --full-name, recursive dependency graph, reverse dependency	references/dependency.md
audit, style, test, tests, test-bot, typecheck, tc, create, edit, cat, extract, livecheck, lc, bump, bump-formula-pr, bump-cask-pr, bump-revision, bump-unversioned-casks, bump-compatibility-version, readall, unpack, irb, ruby, sh, prof, rubocop, vendor-gems, update-python-resources, update-perl-resources, generate-man-completions, generate-zap, tap-new, debugger, gist-logs, developer mode, HOMEBREW_DEVELOPER, Sorbet, RuboCop, --strict, --online, --git, --new, --fix	references/developer.md
Cellar, keg, rack, keg-only, opt prefix, opt_prefix, prefix, --prefix, --unbrewed, --installed, symlink, link, unlink, brew link, brew unlink, --overwrite, --force, --HEAD, --dry-run, pour, relocation, staged path, Caskroom, directory layout, HOMEBREW_PREFIX, HOMEBREW_CELLAR	references/cellar.md

Quick Guide

• How do I install, uninstall, or upgrade a package? → references/commands.md
• How do I write or modify a formula? → references/formula.md
• How do I write or modify a cask? → references/cask.md
• How do I manage taps? → references/taps.md
• How do bottles work and how do I create one? → references/bottle.md
• How do I manage background services? → references/services.md
• How do I use Brewfiles and brew bundle? → references/bundle.md
• What environment variables does brew recognize? → references/environment.md
• How do I clean up, diagnose, or troubleshoot? → references/maintenance.md
• How do I inspect dependencies? → references/dependency.md
• What developer commands are available (audit, test, style, livecheck)? → references/developer.md
• How does the Cellar and keg linking work? → references/cellar.md
• How do I search for packages? → references/commands.md
• How do I pin packages or check what's outdated? → references/maintenance.md
• What's the difference between a formula and a cask? → references/formula.md and references/cask.md
• How do I set up brew in my shell? → references/commands.md (shellenv)
• How do I create a PR to update a formula or cask? → references/developer.md
• What are the global cask directory flags (--appdir, --fontdir, etc.)? → references/cask.md

Cross-Project References

• For Ruby language fundamentals (classes, blocks, DSLs, gems, Bundler), consult Ruby's official documentation — brew's formula and cask DSLs are Ruby-based.
• For Git internals (cloning, remotes, branches, PRs), use the git skill.
• For carapace completion integration (the brew completer in carapace-bin, specs, actions, macros), see the carapace skill.
• For launchd and systemd internals (plist format, unit files, service management beyond brew's wrapper), consult Apple's and systemd's official documentation — this skill covers only brew's services abstraction layer.