Ship in a weekend · EN & DE
The Next.js SaaS starter kit for creators & indie founders.
Cairn is a production-ready Next.js starter for creators and micro-founders selling courses, presets, templates or memberships: auth, Stripe billing, a shop for digital products, transactional email and a bold English and German marketing site, with privacy-first defaults. Spend the weekend building your product, not plumbing.
One-time payment · unlimited projects
- from download to running locally
- ~10 min
- from download to running locally
- site, dashboard and emails
- EN + DE
- site, dashboard and emails
- tracking cookies by default
- 0
- tracking cookies by default
- App Router, React 19, TypeScript
- Next.js 16
- App Router, React 19, TypeScript
Built with Cairn
Devventura: Learn to code by doing the actual job.
Devventura puts you in a fictional company as a junior developer: you read the tickets, write a design note, build the project on your own machine against real tests, and review it like a senior engineer would.
01 / What's inside
Everything a SaaS needs on day one
The boring parts done right, so you can start with the part that makes you money.
Marketing site
- Landing page with hero, features, testimonials, pricing and FAQ
- Shop with product pages for digital products
- MDX blog and contact page
- Light and dark theme
Authentication
- Email and password, magic link, Google sign-in
- Password reset and email change
- Account deletion
- Powered by Better Auth
Dashboard
- Sidebar layout with launch checklist
- Purchases, billing and settings
- Data export for your users
- Admin user list
Payments
- Stripe Checkout for subscriptions, one-time plans and shop products
- Customer portal
- Signed, idempotent webhooks
- hasAccess() helper to gate features
- Welcome, magic link, password reset and verification
- Receipt and failed-payment emails
- React Email + Resend, in English and German
SEO
- Metadata helpers and hreflang
- Open Graph images
- Sitemap, robots.txt and JSON-LD
Developer experience
- One-command setup with seed data and demo accounts
- Validated environment variables
- Postgres via Docker or Docker-free (PGlite)
- Vitest, Playwright and GitHub CI
Launch guide
- Step-by-step launch roadmap in the README
- Reference tags that jump straight to the right code
- Docs for auth, billing, email, deployment and legal
02 / Made in the EU
Privacy-first defaults, built for European customers
Cairn is designed for the rules your customers in Germany and the EU expect.
No cookie banner needed
Out of the box, Cairn sets no tracking cookies and loads no third-party scripts. Visitor stats use a cookieless wrapper for Plausible or Umami.
English and German built in
Marketing site, dashboard and every email exist in both languages, with proper hreflang and no locale cookie.
GDPR features included
Users can export their data and delete their account themselves. Fonts are self-hosted.
EU hosting friendly
Works with Postgres in an EU region, for example on Neon or Supabase, and deploys to Vercel or your own server.
03 / Tech stack
Modern, popular and well documented
No exotic choices: every part is widely used, so answers are easy to find and developers are easy to hire.
- Next.js 16
- React 19
- TypeScript
- Tailwind CSS 4
- shadcn/ui
- Postgres + Drizzle
- Better Auth
- Stripe
- Resend
- Vitest
- Playwright
04 / Who it's for
Made for people who want to launch, not configure
A great fit for
- Creators and micro-founders selling courses, presets, templates or subscriptions
- Developers who want a clean, typed and tested foundation
- Businesses that need an English and German product site
- First-time founders: the launch roadmap explains every step
Good to know
- You need a Postgres database; free tiers at Neon or Supabase are enough to start.
- Payments run through Stripe, and emails through Resend.
- The legal page templates are a starting point, not legal advice.
05 / Licence & delivery
Buy once, build as many projects as you like
One licence covers everything. You get the full source code as a download and in a private GitHub repository.
You may
- Use Cairn for unlimited projects, personal or commercial
- Build products for clients
- Change the code however you like
You may not
- Resell or share Cairn itself as a template, starter or boilerplate
- Publish the source code of Cairn publicly
How you get it
- 1Buy Cairn through the secure Polar checkout.
- 2Open Polar's customer portal (the link is in your receipt email): download the code as a ZIP file, or connect your GitHub account to get the private repository.
- 3Unzip or clone it and run pnpm run setup.
Cairn
One-time payment · unlimited projects
Secure checkout by Polar, our reseller. You get an invoice with VAT and access to the private GitHub repository right after paying.
14-day refund as long as you haven't accessed the repository. Refund policy
06 / FAQ
Questions about Cairn
Do I need to be a developer?
Basic coding knowledge helps. The README contains a launch roadmap that walks you through every step, from running it on your computer to going live. Experienced developers have it running locally in about ten minutes.
Can I use Cairn for client projects?
Yes. One licence covers unlimited projects, including products you build for clients. You may not resell Cairn itself as a template.
Where can I host it?
On Vercel or any server that runs Node.js, plus a Postgres database such as Neon or Supabase in an EU region. The docs cover both Vercel and self-hosting.
Does it work before I set up Stripe and Resend?
Yes. Without a Resend key, emails are printed in your terminal. Without Stripe keys, everything except checkout and the customer portal works. Add the keys when you're ready.
Can I get a refund?
Yes, within 14 days of your purchase, as long as you haven't accepted the repository invitation or downloaded the code. After access, you can contact us about defects or other problems, and your statutory rights apply. See our refund policy for details.
How do I get updates?
Updates are pushed to the private GitHub repository you're invited to after your purchase, so you can pull them like any other change.
Is Cairn GDPR compliant?
Cairn has privacy-first defaults: no tracking cookies, no third-party scripts, self-hosted fonts, data export and account deletion. Whether your product is compliant also depends on how you use it, and you need your own imprint, privacy policy and terms. The included templates are not legal advice.
Launch your SaaS this weekend
Get Cairn, follow the roadmap, and spend your time on the product your customers pay for.