Using Cloudflare with custom domains on Vercel requires some minor steps to work correctly, this depends on whether the domain is being used with or without a proxy.

Without Proxy (DNS only)

In this method, you need to insert a CNAME record with the value cname.vercel-dns.com.

A Cloudflare CNAME record that is not using a proxy.

Following this method will guarantee the speed and reliability of your domain since Vercel will handle the subdomain.

Note: CNAME flattening is a supported feature, however, it will impact the performance of your root domain. We recommend users to redirect the root domain (example.com) to the www subdomain (www.example.com) when possible.

With Proxy

If your domain does require the Cloudflare's proxy to be turned on by default, only one requirement is needed:

  • The domain must allow HTTP requests (without HTTPS) to the path /.well-known/**.

A Cloudflare CNAME record that is not using a proxy.

To verify if that is possible with your domain, you can run the following command (notice the http:// part in the URL):

curl http://example.com/.well-known/acme-challenge -I

A configuration that does allow Vercel to run smoothly would return the following:

curl http://example.com/.well-known/acme-challenge -I
HTTP/1.1 404 Not Found

If you run the curl command and receive a 3XX redirect instead, Cloudflare is preventing this route from being accessed, and Vercel will mark the domain as not configured:

curl http://example.com/.well-known/acme-challenge -I
HTTP/1.1 404 Moved Permanently

You need to explore the following configuration in the Cloudflare dashboard:

  • Page Rules — You can disable HTTPS for the path /.well-known/**.
  • Always use HTTPS — This configuration is under the "SSL/TLS" tab and it may affect your page rules.
  • Other Configurations — Cloudflare can offer multiple settings and this will directly affect Vercel's ability to generate certificates.
Note: Vercel cannot offer Cloudflare-specific support. If you are facing difficulties with your Cloudflare managed domain, please reach out to their support at https://support.cloudflare.com.