Cypress gets 404 on Render subdomains

I have a peculiar issue, where my tests are failing only on Render subdomains.

I’ve created a Github action, which triggers Cypress to run end-to-end tests on our app. For some reason, this results in a 404, even though the app is perfectly alive and accessible during normal browsing.

I’ve narrowed it down to affect only subdomains hosted on Render, e.g. and

The tests run fine if:

  • I set the URL to be the top domain (i.e. or a subdomain not hosted on Render (e.g.
  • I access the underlying URL, e.g.
  • I run the same tests locally

As far as I can see, the DNS is set up correctly, with a CNAME record pointing to the subdomain, as outlined in the documentation.

Considering it’s actually a 404, and not a timeout, it seems the app is actually hitting a gateway (or something) which then immediately returns 404.

Where do I go from here?

Hi @nixstrom, if you are using subdomains, you’ll need to configure a wildcard custom domain: Custom Domains | Render · Cloud Hosting for Developers. This will require you to add 2 CNAME records to your DNS settings - one for the wildcard and a second _acme-challenge one.