nextjs-saas-starter

Blank-slate Next.js SaaS scaffolding with Mailtrap as the email layer, Supabase auth, and Stripe billing.

For learners, indie hackers, and juniors — not production-grade multi-tenant SaaS.

Prerequisites

• Node.js 20+
• pnpm 10+
• Docker Desktop (for local Supabase)
• Stripe CLI (for local billing webhooks)
• Mailtrap account (API token + Email Testing inbox + hosted templates)

Quick start (local)

git clone https://github.com/mailtrap/nextjs-saas-starter.git
cd nextjs-saas-starter
pnpm install
pnpm db:setup          # Docker: Supabase Auth + Postgres + schema → writes .env.local

Copy remaining values from .env.example into .env.local:

1. Mailtrap — API token, sandbox inbox ID, from address, 8 template UUIDs
2. Stripe — secret key, webhook secret (from Stripe CLI below), Pro + Team price IDs
3. Admin — your email in ADMIN_EMAILS (for /admin/emails)

Optional Stripe test products/prices:

stripe fixtures stripe-fixtures.json --api-key "$STRIPE_SECRET_KEY"

Start the app (port comes from NEXT_PUBLIC_APP_URL):

pnpm dev

Open the URL in .env.local (default http://127.0.0.1:3000).

Port / URL configuration

NEXT_PUBLIC_APP_URL is the single source of truth for:

• Next.js dev port (pnpm dev)
• Supabase site_url and auth redirects
• Send Email Hook URI (Docker → host app)

If port 3000 is taken, set e.g. NEXT_PUBLIC_APP_URL=http://127.0.0.1:3001, then:

pnpm sync:env
pnpm db:stop && pnpm db:start
pnpm dev

What pnpm db:setup does

1. Starts only Supabase Auth + Postgres (not Storage, Studio, Realtime, etc.)
2. Applies supabase/migrations/ (source of truth for schema)
3. Writes Supabase credentials into .env.local
4. Syncs auth hook URL and redirect URLs from NEXT_PUBLIC_APP_URL

Stop Docker: pnpm db:stop · Reset database: pnpm db:reset · Restart: pnpm db:start

Cloud Supabase instead of Docker

Create a project at supabase.com, run SQL from supabase/migrations/, copy API keys into .env.local, and configure:

• Auth → URL → your NEXT_PUBLIC_APP_URL
• Auth → Hooks → Send Email → https://YOUR_APP/api/auth/send-email

Local webhooks

Stripe (required for billing sync)

In a second terminal (use the port from NEXT_PUBLIC_APP_URL):

stripe listen --forward-to localhost:3001/api/webhooks/stripe --api-key "$STRIPE_SECRET_KEY"

Copy the webhook signing secret into STRIPE_WEBHOOK_SECRET in .env.local.

Mailtrap (optional locally — no ngrok needed)

Set MAILTRAP_WEBHOOK_SECRET in .env.local, then simulate an event:

pnpm webhook:test:mailtrap

Refresh /admin/emails to see the test event. In production, point Mailtrap webhooks at https://YOUR_APP/api/webhooks/mailtrap.

Env vars

Full list: .env.example

Mailtrap sandbox (recommended for local dev)

MAILTRAP_SANDBOX=true
MAILTRAP_ACCOUNT_ID=12345           # optional, silences SDK warning
MAILTRAP_TEST_INBOX_ID=123456       # Email Testing → inbox settings
MAILTRAP_WEBHOOK_SECRET=your-secret # local: any string; match in Mailtrap dashboard for prod

Emails appear in your Mailtrap Email Testing inbox, not the recipient's real mailbox. Set MAILTRAP_SANDBOX=false before production deploy.

Architecture

src/app/          → routes (marketing, auth, dashboard, API webhooks)
src/actions/      → Server Actions (auth, billing, org, settings)
src/lib/mailtrap  → sendEmail(), webhook signature verify
src/config/emails → typed template UUID map
src/db/           → Drizzle schema (profiles, orgs, subscriptions, email events)

Email flows: Supabase Send Email Hook → Mailtrap (magic link, password reset, email change). App events → sendEmail() (welcome, invites, billing).

Billing: Stripe Checkout for upgrades; downgrades cancel or update the existing subscription via changePlan().

Where to add your product logic

1. Create src/features/your-feature/ — see src/features/README.md
2. Add a route under src/app/dashboard/your-feature/page.tsx (or another app route)
3. Call sendEmail() from @/lib/mailtrap for new transactional emails

Scripts

pnpm db:setup              # first-time local setup (Docker + migrations + .env.local)
pnpm db:start              # start Supabase + reset + sync env
pnpm db:stop               # stop Docker Supabase
pnpm db:reset              # re-apply supabase/migrations
pnpm sync:env              # sync Supabase auth URLs from NEXT_PUBLIC_APP_URL
pnpm dev                   # Next.js dev server (port from NEXT_PUBLIC_APP_URL)
pnpm build && pnpm start   # production build
pnpm lint
pnpm typecheck
pnpm test                  # unit tests (vitest)
pnpm test:e2e              # Playwright
pnpm webhook:test:mailtrap # local Mailtrap webhook test (no ngrok)
pnpm lighthouse            # Lighthouse CI

Schema changes: edit supabase/migrations/, then pnpm db:reset. The drizzle/ folder mirrors schema for Drizzle ORM queries; db:generate / db:push are optional and not used by default setup.

Post-deploy checklist

1. Run supabase/migrations/ SQL on production Postgres (or link hosted Supabase)
2. Set all env vars from .env.example
3. Stripe → Webhooks → https://YOUR_APP/api/webhooks/stripe
4. Mailtrap → Webhooks → https://YOUR_APP/api/webhooks/mailtrap
5. Supabase → Auth → Hooks → Send Email → https://YOUR_APP/api/auth/send-email
6. Paste Mailtrap template UUIDs and verify sending domain
7. Set ADMIN_EMAILS for admin access

License

MIT