TL;DR: # Cloudflare for SaaS: custom hostnames Cloudflare for SaaS extends your Cloudflare security and performance to customer-owned domains: your customers add their hostname to your zone as a custom hostname, and their traffic routes through your configuration to your origin. ## Fallback origin Custom hostnames route to a **fallback origin**: the default origin server for hostnames that do not match a more specific route.

## Fix
1. Set it before onboarding customers; it is the safety net that answers when a hostname has no dedicated origin configured.
   Expected: this specific failure stops.
2. Available on all plans. ## The apex limitation Customers typically point their domain at you with a CNAME, but DNS forbids CNAME at the apex.
   Expected: this specific failure stops.
3. Supporting customer apex domains requires **apex proxying**, an Enterprise add-on (or BYOIP on Enterprise).
   Expected: this specific failure stops.
4. Plan for this in pricing conversations before a customer asks "why can't I use my root domain". ## Onboarding sequence 1.
   Expected: this specific failure stops.
5. You verify the hostname status is active before sending them traffic.
   Expected: this specific failure stops.

## Details
2. Customer completes domain control validation (DNS record at their provider). 3. 4.

## When to use
You hit exactly this: Cloudflare for SaaS custom hostnames: fallback origin and apex limits in Cloudflare for SaaS custom hostnames.

## When not to use
A different error, or the same symptom in a different tool. This page only covers the failure above.

## Compatibility
Cloudflare for SaaS custom hostnames.

## Edge cases
- Customer adds the custom hostname in your flow (API or dashboard).
- Monitor: a customer who breaks their validation record later degrades silently. ## Checklist - Fallback origin configured and answering correctly before the first customer. - Validation status checked programmatically for every hostname; alert on anything not active. - Document the apex story for customers up front.