Vercel Platforms Starter Kit in 2026: what it ships and what you still build
The Vercel Platforms Starter Kit is a free, open-source Next.js template that gives you subdomain multi-tenancy on Vercel: each tenant gets tenant.yourdomain.com behind one wildcard DNS record. What it does not ship is support for customer-owned domains. Verification flows, SSL edge cases, monitoring, and an API for it are yours to build.
That gap is the whole story of this post. The kit is good at what it does, it costs nothing, and on raw per-domain fees Vercel beats every managed provider, including us. Full disclosure up front: Domainee is a custom domains API for SaaS with a native MCP server — 50 domains and 100 GB free. So the useful comparison is not "kit vs API". It is an itemized ledger of what sits between cloning the repo and running a production custom domains feature, priced honestly on both sides.
What the starter kit actually includes
The current kit (the vercel/platforms template, roughly 6,700 stars) is a Next.js 16 App Router project with React 19, Tailwind 4, and Upstash Redis as the tenant store. Tenancy is subdomain-based. A proxy layer reads the subdomain out of the incoming host header, looks up the tenant under a subdomain:{name} key in Redis, and renders that tenant's content. You also get an admin screen for managing tenants and a local-dev setup that fakes subdomains on localhost.
Production setup per the README is two steps: point your root domain at Vercel, add a wildcard record for *.yourdomain.com. Vercel issues the wildcard certificate, with one catch we cover below. For a hackathon project, an internal tool, or the subdomain phase of a young SaaS, this is a great starting point. It costs nothing beyond your Vercel plan.
Subdomains are not custom domains
Here is the distinction the search results blur. The kit gives every tenant a subdomain of YOUR domain: acme.yourapp.com. A custom domains feature is your customer bringing THEIR domain: app.acme.com, or acme.com itself. The kit's README stops at the wildcard record and never touches the second case.
The second case is what customers ask for the moment they pay you real money. It is also a different engineering problem. A wildcard cert on your own domain covers every subdomain tenant at once. A customer domain needs individual DNS instructions, per-domain verification, a certificate issued and renewed for that exact hostname, and something watching it afterward, because customers change DNS records without telling you.
What Vercel gives you beyond the kit
To be fair to the platform: Vercel itself, as opposed to the starter kit, has real support for customer domains, sold under the Vercel for Platforms umbrella. The relevant facts as of mid-2026:
- Custom domains cost $0. Vercel does not meter them. Hobby caps you at 50 domains; Pro and Enterprise are unlimited, with soft anti-abuse caps of 100,000 and 1,000,000 domains per project.
- SSL is automatic for verified domains on all plans. Bring-your-own certificates, the thing a tenant with compliance requirements eventually asks for, are Enterprise-only.
- Wildcard domains require Vercel's nameservers. If your root domain's DNS lives at Cloudflare or Route 53 and you want the kit's wildcard setup, you are moving nameservers.
- The domain APIs are rate-limited: 100 domain additions per hour per team, 50 verifications, 100 removals.
- Platform Elements ship prebuilt pieces, like an Add Custom Domain server action and a DNS-instructions table, so you write less glue.
If your app runs on Vercel and will stay there, that is a solid foundation. Notice the lock-in shape, though. All of it, from the wildcard nameserver requirement to the domain API, assumes Vercel is your host. The kit's routing trick and the Platforms domain layer do nothing for an app on AWS, Fly, Railway, or a second product on different infrastructure.
The build ledger: kit to production
This is the part nobody prices. Between "cloned the starter kit" and "customer domains in production" sits a list of jobs, and every team that rolls their own ends up building the same ones:
| Job | What it involves |
|---|---|
| Verification UX | Generate per-domain TXT/CNAME instructions, poll until propagated, handle the apex-vs-subdomain split |
| Cert edge cases | CAA records blocking issuance, DNS-01 challenges for wildcards, renewal failures at 3am |
| Health monitoring | Detect when a customer silently repoints DNS, expire state, notify them, not you |
| Webhooks | Your billing and onboarding flows need domain lifecycle events to react to |
| Bulk onboarding | At 100 additions/hour, migrating 2,000 customer domains is a 20-hour scripted job with retry logic |
| Your own API surface | If customers or their AI agents configure domains programmatically, you now maintain a public API |
| Support tooling | Someone asks "why is my domain not working" weekly; support needs a diagnosis screen |
None of these is hard on its own. Together they are a quarter of platform-engineering work, then a permanent maintenance rotation. The Next.js multi-tenant guide walks the routing half of this in code. The list above is everything around it.
DIY on Vercel vs a managed API
| Starter kit + Vercel for Platforms | Domainee | |
|---|---|---|
| Per-domain price | $0 (Hobby capped at 50) | 50 free, then $0.20/mo graduated down to $0.10 |
| Works off Vercel | No, Vercel-hosted apps only | Yes, any host |
| Wildcard on your domain | Yes, requires Vercel nameservers | Yes |
| Customer BYO domains | You build verification, monitoring, API | One POST /domains call, SSL included |
| Custom SSL certs | Enterprise plan only | Included |
| Health monitoring + webhooks | You build it | Included, HMAC-signed |
| AI-agent surface | None | Native MCP server |
| Engineering cost | The ledger above, plus maintenance | An afternoon of integration |
On pure unit economics: if you are Vercel-hosted, small, and have engineering time to spend, DIY wins on the invoice and loses on the ledger. Run your own numbers in the cost calculator. The broader API comparison prices the managed alternatives against each other at 25, 100, and 500 domains.
When the starter kit is the right call
An honest list, because it is a good template:
- You are all-in on Vercel and expect to stay. The nameserver and hosting coupling costs you nothing.
- Subdomain tenancy is enough for now. Nobody has asked to bring their own domain yet, and building for a request that has not arrived is how platform teams burn quarters.
- You have platform engineers who own infrastructure as their job and would happily own the ledger above.
- Your domain count is small and stable. Under Hobby's 50-domain cap the whole thing is free.
When a managed API wins
- Your origin is not (only) Vercel. Multi-cloud, a legacy app, or a second product means the Platforms layer cannot follow you.
- Customers bring their own domains and expect verification UX, fast SSL, and support that just works.
- You need lifecycle events: webhooks into billing, monitoring that emails the customer instead of paging you.
- Agents are part of your product. If AI assistants configure domains for your users, an MCP-native domain API is the difference between a tool call and a scraping hack.
- You might sell domains in-app later. That is an entirely separate build on Vercel and a single API family with us.
FAQ
Is the Vercel Platforms Starter Kit free? Yes. It is an open-source Next.js template, free to clone and deploy. Your costs are the Vercel plan it runs on (Hobby is free, Pro is $20 per member per month), usage-based bandwidth, and the engineering time to extend it beyond subdomain tenancy.
Does the starter kit support customer custom domains? Not out of the box. The current kit implements subdomain-based multi-tenancy on your own domain via a wildcard DNS record. Supporting domains your customers own requires the Vercel domain APIs plus verification, SSL handling, and monitoring you build yourself.
How many custom domains does Vercel allow? 50 on Hobby. Pro and Enterprise are unlimited, with soft anti-abuse limits of 100,000 and 1,000,000 domains per project that Vercel can raise on request. Domain API calls are rate-limited to 100 additions per hour per team.
Why does wildcard SSL require Vercel nameservers? Wildcard certificates are only issued via a DNS-01 challenge, which requires the certificate authority to see a TXT record Vercel controls. Delegating your nameservers lets Vercel write that record automatically. A wildcard certificate then covers all tenant subdomains at once.
Can I use the starter kit if my app is not hosted on Vercel? The routing pattern is portable Next.js, but everything domain-related, from wildcard SSL to the domain APIs and Platform Elements, assumes Vercel hosting. Off Vercel you would pair your own host with a provider-neutral custom domains API, and check DNS moves with a propagation checker during migration.