tl;dr you can use * to resolve any domain you like to

Using a wildcard domain for localhost

There are certain situations where you might be working in an environment that requires a locally virtual-hosted environment but a domain that looks like a real-world one. For example, you might be working on an OAuth client where the server wants you to have an actual domain name for the callback URL.

On a lot of systems, *.localhost will resolve and the SSO server will allow you to add this as a callback URL, which is fine. However, this may not be enough when:

  • You need to virtual-host several systems locally, so need multiple domains.
  • Your system doesn’t resolve *.localhost (e.g. Debian), or:
  • The SSO server only permits localhost, and not subdomains of localhost.

I’ve added a wildcard entry for * on my domain, so this can be used for testing in such an environment which resolbes to Obviously this won’t enable you to make things avalable to other parts of the internet, but will allow you to quickly add a new domain in a development envronment.

This entry is hosted on Cloudflare, so should be pretty accessible.