How to encode external url?

Hello Sir,

I chosen Custom URL prefix. Now, I don’t want to show external link too. How to encode external link?

For example: I given custom prefix as https://mydomain.com/out.php?url=

Now external links became: https://mydomain.com/out.php?url=https://externaldomain.com/

I don’t like to show https://externaldomain.com/ in the url. How can I encode this?

Waiting for solution.

Thank you.