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Every project on Deploy Your App receives an automatically generated subdomain under the platform’s base domain (e.g. my-app.your-base-domain.com). You can also map your own domain — such as app.example.com — to a project by creating a CNAME record in your DNS provider and verifying it through the dashboard. Caddy, the platform’s reverse proxy, handles TLS certificate provisioning automatically via ACME once verification passes.
Custom domains are globally unique across all projects on the platform. If a domain is already registered to another project, the request to add it will be rejected. Each project can have at most one custom domain at a time.

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Steps

1

Add the custom domain

Open your project in the dashboard and go to Settings → Domains. Enter the full hostname you want to use (e.g. app.example.com) in the custom domain field and save.The platform normalizes the value before storing it:
  • Strips https:// or http:// prefixes
  • Removes trailing slashes
  • Lowercases the entire string
The domain is saved to the customDomain field on the Project record in PostgreSQL with customDomainVerified set to false. The domain is not active until verification succeeds.
2

Create a CNAME record in your DNS provider

Log in to your DNS provider (e.g. Cloudflare, Route 53, Namecheap) and add a CNAME record pointing your hostname to the platform’s base domain (NEXT_PUBLIC_BASE_DOMAIN).
TypeNameValueTTL
CNAMEappyour-base-domain.com300 (or Auto)
For example, if your domain is app.example.com and the platform base domain is deploy.acme.io, create a CNAME record with name app pointing to deploy.acme.io.
DNS propagation can take anywhere from a few minutes to 48 hours depending on your DNS provider and the TTL of the record. The platform’s verification will fail until the CNAME record has fully propagated.
You can confirm propagation before clicking Verify using dig or nslookup:
dig CNAME app.example.com
# or
nslookup -type=CNAME app.example.com
The output should show your custom hostname resolving to the platform base domain.
3

Verify the domain

Once DNS has propagated, click Verify Domain in the dashboard. This calls POST /api/v1/projects/:id/domain/verify.The server uses Node.js’s dns.resolveCname() (from node:dns/promises) to resolve the CNAME record for your domain and checks that at least one of the returned records matches NEXT_PUBLIC_BASE_DOMAIN (case-insensitive).If verification succeeds:
  • The customDomainVerified flag on the Project record is set to true
  • The platform proxy begins routing traffic for that hostname to your project
  • Caddy starts the ACME certificate provisioning flow for your domain
If verification fails, the API returns an error message showing what the CNAME currently resolves to (e.g. CNAME record does not match deploy.acme.io. Currently points to: old-value.com). Check your DNS settings and try again after propagation.
4

TLS is handled automatically

You do not need to provision or upload any TLS certificates. Caddy automatically obtains a certificate for your custom domain via the ACME protocol (Let’s Encrypt or ZeroSSL) once the domain is verified and traffic is routed through the proxy.The platform exposes a /_internal/tls-check endpoint that Caddy uses to confirm a domain is registered and verified before initiating certificate issuance. This prevents certificates from being issued for domains that haven’t been properly set up.After a short period (usually under a minute), your application will be reachable over HTTPS at your custom domain.

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How the proxy routes custom domains

When an inbound HTTP/HTTPS request arrives at the platform proxy on a hostname that does not match the base domain pattern, the proxy:
  1. Looks up the Project record in the database where customDomain equals the request hostname and customDomainVerified is true.
  2. Reads the project’s metadata.containerId to determine the running Docker container.
  3. Proxies the request to the container’s internal port.
For statically deployed projects (built artifacts stored in Cloudflare R2), the proxy routes the request to the correct R2 bucket path instead of a container.

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Removing or changing a custom domain

To remove a custom domain, clear the custom domain field in Settings → Domains and save. The customDomain field is set to null and customDomainVerified is reset to false. The platform proxy stops routing traffic for that hostname immediately. Caddy will not renew the TLS certificate on its next renewal cycle. To switch to a different domain, enter the new hostname, save, then follow the CNAME and verification steps above for the new domain.

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