Tooling

The Firefox build/dev toolchain is large. This page summarizes the moving parts that contributors interact with.

mach: the unified driver

The top-level mach script (with mach.cmd and mach.ps1 for Windows) is implemented in python/mach/. It autoloads mach_commands.py files from across the tree, where commands like build, test, lint, vendor, etc., are registered as Python decorators.

./mach help lists every available command. ./mach <command> --help describes one.

mozbuild: the build engine

python/mozbuild/ is the engine that interprets moz.build, moz.configure, and friends to produce the actual Makefiles and ninja files used during compilation.

Stages of a build:

1. ./mach configure — runs moz.configure, writes config.status and mozinfo.json.
2. ./mach build-backend — reads all moz.build files, generates Makefiles in <objdir>/.
3. ./mach build — runs make (which delegates to clang, rustc, javac, etc.).
4. ./mach package (release builds) — assembles a shippable tar/dmg/zip.

Configure system

moz.configure files use a Python-with-decorators DSL. Top-level moz.configure imports per-subsystem config files (build/moz.configure/*.configure, etc.). Options become available as --enable-foo / --with-foo flags and as ac_add_options lines in .mozconfig.

Linters

./mach lint orchestrates a suite of linters via tools/lint/:

• eslint — JS lint, configured via eslint.config.mjs plus the per-directory configs (eslint-file-globals.config.mjs, eslint-ignores.config.mjs, eslint-rollouts.config.mjs, eslint-subdirs.config.mjs, eslint-test-paths.config.mjs).
• prettier — formatter for JS/CSS/JSON.
• stylelint — CSS lint.
• clang-format — C/C++ formatter.
• clang-tidy — selected C++ checks.
• rustfmt + clippy — Rust.
• ruff, black — Python.
• codespell — typo checker.
• mots — module ownership consistency.
• license — header / SPDX consistency.

Code generators

Generator	Input	Output
xpidl (xpcom/idl-parser/)	*.idl	C++ headers, typelibs, JS bindings
WebIDL bindings (dom/bindings/)	*.webidl	C++ binding glue (JS ↔ C++)
IPDL (ipc/ipdl/)	*.ipdl	C++ actor classes (*Parent, *Child)
Glean YAML (toolkit/components/glean/)	metrics.yaml, pings.yaml	C++/JS metric APIs
uniffi-bindgen-gecko-js (toolkit/components/uniffi-bindgen-gecko-js/)	Rust UniFFI components	JS bindings to Rust
mozbuild backend (python/mozbuild/)	moz.build	Makefiles / ninja
StaticPrefs (modules/libpref/init/StaticPrefList.yaml)	YAML	C++ accessor headers

Vendoring

Third-party Rust crates live under third_party/rust/ and are managed via:

./mach vendor rust

This reads Cargo.toml, downloads crates, runs the supply-chain audit, and regenerates lockfiles. The audit policy lives in supply-chain/ (config.toml, audits.toml, imports.lock).

NPM dependencies for ESLint/prettier/etc. are pinned in package.json and package-lock.json. Mozilla does not use npm for runtime dependencies.

TaskCluster

taskcluster/ defines what runs in CI. Highlights:

• taskcluster/config.yml — global config.
• taskcluster/kinds/ — one directory per "kind" (build, test, l10n, …) with task definitions.
• taskcluster/gecko_taskgraph/ — the Python task-graph generator.
• taskcluster/android_taskgraph/ — Android-specific generator.
• taskcluster/docker/ — Dockerfile and tarball builders for CI workers.
• taskcluster/scripts/ — entry-point scripts run inside CI containers.

The decision task on every push reads these files, generates the task graph, and submits it to TaskCluster.

try: the previewing branch

./mach try pushes a snapshot of your tree to a special branch (try) where TaskCluster runs your selected subset of tests. Selectors include:

• ./mach try fuzzy — interactive selection.
• ./mach try auto — heuristic auto-selection.
• ./mach try chooser — full taxonomy picker.
• ./mach try empty — bare push (just for try server side-effects).
• ./mach try syntax -b do -p all -u all -t none — syntax-style selectors.

Results display on Treeherder.

Other notable tooling

• ./mach watch — incrementally rebuild on file change.
• ./mach addtest — scaffolding for new test files.
• ./mach analyze — static-analysis runs.
• ./mach python <script> — run any tree script with PYTHONPATH set.
• ./mach python-test — run Python unit tests.
• ./mach setup / ./mach bootstrap — toolchain setup.
• ./mach install — install the built browser somewhere.
• ./mach tps — Sync TPS tests.

Editor integrations

• VS Code — Mozilla provides a workspace via ./mach ide vscode. Includes recommended extensions and clangd config.
• Other — ./mach ide eclipse, ./mach ide visualstudio (Windows), etc.