A tour of the folders

Know where things live before you change them. Most of the repository is Arc CMS itself (core); a small set of folders and files belongs to your app (the custom space).

The "Kind" column below is the same sorting npm run check:core uses: core is Arc CMS's own code, custom is your app's, and install is the settings of one installation. In an app built on a copy of Arc CMS, you change custom and install files only. Core and custom explains the rule.

The browser app

Path	Kind	What it holds
`src/app/`	Core	The Angular app. `src/app/pages/` holds the pages, found by file name (AnalogJS file-based routing), `src/app/app.routes.ts` the routes that need to be listed by hand, `src/app/core/` the services every page uses (install settings, features, languages, the installable app) and `src/app/guards/` the route guards.
`src/shared/`	Core	Building blocks shared by the pages: components (such as the table and the page header), services, models, constants and the email compiler.
`src/custom/`	Custom	Your app's pages, routes, admin menu items and changes to both menus, member dashboard, landing pages per role, translations, styles, installable app settings and feature choices (`src/custom/features.ts`).
`src/environments/`	Install	The Firebase web config for each build (`src/environments/environment.ts`, `src/environments/environment.prod.ts`, and one `firebase-web.<projectId>.ts` per project once you fetch them) and `src/environments/arc-install.ts`. `npm run arc:configure` writes the generated ones; you edit only `environment.ts` and `environment.prod.ts`.
`src/assets/`, `src/styles/`	Core	Files bundled into the app, such as the interface translations in `src/assets/i18n/`, and the global styles.
`src/test/`	Core	Test setup and the providers that page tests share.
`index.html`	Core	The page the app starts in. It loads `src/custom/styles.css` last, so your styles win.

The server side

Path	Kind	What it holds
`functions/src/`	Core	The Cloud Functions, one folder per area (`functions/src/users/`, `functions/src/search/`, `functions/src/pages/` and so on). `functions/src/all.ts` lists every function, `functions/src/features/` the functions of each switchable feature, and `functions/src/__tests__/` their tests.
`functions/src/custom/`	Custom	Your app's own functions and triggers, the callables the deploy checks, and the collections your app makes searchable.
`functions/scripts/`	Core	Helpers the deploy runs: publishing the generated pages and checking that callables are reachable.
`firestore.rules`, `storage.rules`, `firestore.indexes.json`	Core	Arc CMS's security rules and database indexes.
`firestore.app.rules`, `storage.app.rules`, `firestore.app.indexes.json`	Custom	Your app's rules and indexes. They are optional: create them when your app has data of its own. Every deploy combines them with the core files (see Set security rules and indexes).
`firebase.json`	Core	The Firebase CLI config: the `arccms` functions codebase, the rules and index files, and the hosting settings.

The public site

Path	Kind	What it holds
`public/`	Core	Files served on the site as they are: Arc CMS's default website in `public/_site/` (content templates, sample static pages, the sample header and footer, translations), including the placeholder home page, and assets. A website puts its own home page, templates, pages, header and footer in `src/custom/site/` instead, which replace these; `npm run check:core` counts a change here as a core change. See Design templates.

Tooling, tests and docs

Path	Kind	What it holds
`scripts/`	Core	The command-line tools behind the npm scripts: the guided deploy, `arc:configure`, the rules build, `check:core`, the docs tools, and a helper `vite.config.ts` uses to build with less memory. See npm scripts. Also `scripts/arc-admin-script.mjs`, which your own scripts use to reach Firebase.
`custom/`	Custom	Your app's command-line scripts, the data they import, and design files. Not bundled into the site. See Run scripts and keep data.
`tests/rules/`	Core	Tests of the combined security rules, run with `npm run test:rules`.
`tests/rules/custom/`	Custom	Your app's own rules tests.
`docs/`	Core	This developer documentation.
`docs/custom/`	Custom	Your app's own docs.
`.github/`	Custom	Your app's CI workflows. Arc CMS ships none. See Deploy from CI.
`package.json`, `functions/package.json`	Core, reviewed	The dependency lists and npm scripts. An app may add dependencies; `npm run check:core` lists the change for a look but allows it.
`vite.config.ts`, `angular.json`, `tsconfig.json`, `vitest.config.ts`	Core	Build and test configuration.

Files you will not find in the repository

Some files are made per checkout and are not committed:

.firebaserc: your Firebase project aliases, written by firebase use --add.
arccms.config.json: the install settings of each Firebase project (copy arccms.config.example.json to start). See Configure a project.
firebase.{projectId}.json and functions/.env.{projectId}: generated from arccms.config.json by npm run arc:configure and by the guided deploy.
.arc-build/: the combined rules and indexes, built before every deploy.
.arc-deploy-state.json: what the guided deploy remembers about your last deploys.
functions/src/*.gen.ts: the list of features the functions build includes, generated from src/custom/features.ts before every functions build.