Is it safe to use protocol relative URL in email?

Question

There are existing discussion [1] on the use of protocol relative URL in HTML, but how about email?

Will email client, or service providers like Gmail strip or modify pr

Answer 1

No , its not safe to use protocol relative URL in email. because its change protocol so that browser can fetch a resource from whatever protocol the site is telling it to use.

but some email clients (Outlook especially, as usual) won’t try to use HTTP or HTTPS as the protocol. Instead they’ll use the file:// protocol and assume the resource you’re referring to is on the local machine. But it won’t be. So don’t use these in emails. You have to be sure that the server you’re requesting from is capable of serving content over both HTTP and HTTPS. If not you might end up fetching content from an unsecured or nonexistent server port.

IE6 does not know how to handle this. If you care about supporting Internet Explorer 6 then you shouldn’t use these.

IE7-8 support protocol relative URLs but they’ll end up fetching the resource twice. Once from HTTP and once over HTTPS. This can slow things down a bit but the way I see things it’s not much of a problem for anyone except the person using IE7-8 and if you’re using IE you’ve got more important things to worry about.

its browser dependent so its depends what browser you are using GMAIL working fine in crome but not in IE6.