Why I built a SvelteKit + FastAPI SaaS Boilerplate (and open-sourced the starter)

Every SaaS boilerplate on the market is Next.js.

I searched for months. ShipFast, Supastarter, LaunchFast — all Next.js + Supabase or Prisma. Nothing for the SvelteKit + FastAPI stack that I actually build production apps with.

So I built one.

The Stack

• Frontend: SvelteKit 5 (runes syntax), Tailwind CSS v4, TypeScript
• Backend: FastAPI, SQLAlchemy async, Pydantic v2
• Auth: JWT tokens, bcrypt, email verification, password reset
• Billing: Stripe subscriptions (3 tiers), customer portal, webhooks
• Database: SQLite (dev) / PostgreSQL (production)
• Email: SMTP/Brevo with HTML templates
• Deploy: Docker multi-stage build, nginx reverse proxy

What's Included

50+ files extracted from two production SaaS apps I run (a construction management platform and an EHCP tracker for parents).

• Multi-tenant authentication with role-based access control (user / admin / superadmin)
• Stripe subscription billing with checkout sessions, webhooks, and customer portal
• Admin dashboard with user management and system stats
• Landing page with animated pricing table
• Dark theme with 6-level surface hierarchy and configurable accent color
• Docker Compose for one-command production deployment

Why SvelteKit + FastAPI?

SvelteKit 5 with runes is genuinely faster to build with than React. $state, $derived, $effect — no useState/useEffect ceremony. The compiled output is smaller and faster.

FastAPI gives you automatic OpenAPI docs, type validation via Pydantic, and async by default. Combined with SQLAlchemy, you get a backend that's both fast to write and fast to run.

Docker ties it together. One docker compose up -d and you have a production-ready app with nginx, SSL, health checks, and security headers.

Free Starter vs Premium

I open-sourced a lite version with JWT auth, dark theme, and Docker deploy:

Free: github.com/Quartalis/sveltekit-fastapi-starter

The premium version adds Stripe billing, admin dashboard, multi-tenancy, email verification, password reset, and RBAC:

Premium: quartalis.co.uk/store/saas-boilerplate

Live Demo

You can see the starter kit running at demo-saas.quartalis.co.uk — try creating an account and logging in.

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If you're building SaaS with SvelteKit + FastAPI, I'd love to hear what you'd want in a boilerplate. The premium version is still evolving and I'm adding features based on what developers actually need.