Ages ago we included a redirect in web.config to ensure that pages would rewrite to http://www.example.com/ if the user input, say, www.example.comor variants of it.
Recently we changed the site so its (finally) going to HTTPS. So the rewrite should do the same but this time to https://www.example.com/
We used this, note it's permanent:
<action type="Redirect" url="http://www.example.com/{R:1}" redirectType="Permanent" />
As it was permanent, what happens if we change that to HTTPS?
When you use a 301 (permanent) redirect, the browser caches this redirection and uses it further on. So the change won't be visible for people that have already visited the URL before since they are going to be redirected to the HTTP version that you used in the first place. New visitors will follow the new redirection.
However, a best practice is to force the use of HTTPS for your domain, so I would add a rule to force all HTTP requests to HTTPS (if I'm not wrong IIS URL Rewrite, out of the box, has a template to do that). In that case people that have the old redirection cached won't notice the new one but will end up in HTTPS anyway. It will work with any external link you have pointing to HTTP, etc.
