How to disable Chrome HSTS permanently for a subdomain

On the main domain, you can remove the includesubdomains option of your HSTS header, so it will not redirect the sub domain.

However, this is not the most secure solution. To be effective, it's better to set HSTS+includesubdomains on all your domains and subdomains (or an attacker car fake the domain "http://secure.yourdomain.com" for example).

So the most secure solution is to use a self-signed certificate (or a real one) for your dev domains and import it before in your browsers.

You can type thisisunsafe anywhere on the Google Chrome warning page and it will load it without warning. No joke.