Do I need to use Cloudflare as my DNS provider to connect a free custom domain to Cloudflare Pages, or can I use another registrar's DNS?

While using Cloudflare as your DNS provider (by changing your domain's nameservers to Cloudflare's) is the most straightforward and recommended approach for Cloudflare Pages, it's not strictly mandatory. You can use another DNS provider (e.g., your domain registrar's DNS) to manage your domain. In that case, you would simply add the required CNAME or A records provided by Cloudflare Pages directly into your external DNS provider's settings. However, using Cloudflare DNS provides additional benefits like performance, security features, and automatic SSL provisioning.