What does `//` in javascript's src attribute do?

Question

I'm using Facebook's javascript sdk and it has double forward slashes. What do they mean?

<script src="//connect.facebook.net/en_US/all.js"></script>

I know a single / means root directory, but what is //? Is that telling the source to use http:// and then the path?

See here, http://stackoverflow.com/questions/550038/is-it-valid-to-replace-http-with-in-a-script-src-http — NEO, Mar 13 '13 at 05:11

score 19 · Accepted Answer · answered Mar 13 '13 at 05:12

19

This is a "protocol-relative" link. It uses http or https depending on what was used to load the current page.

answered Mar 13 '13 at 05:12

Thilo

HI @thilo Is it HTML 5 Specific or it will work with HTML 4 browsers too.. – Dilip Rajkumar Dec 19 '13 at 10:47
Can you use it in any other html tag? for instance, as the value for the `href` attribute in `` tags. – Paul Razvan Berg Dec 08 '19 at 18:44

score 2 · Answer 2 · answered Mar 13 '13 at 05:12

2

It makes it protocol agnostic, if your page is served using https: it makes the request using https:

answered Mar 13 '13 at 05:12

kevmc

score 0 · Answer 3 · edited May 23 '17 at 12:24

0

Please find the details in these links this explains why we need double slash

edited May 23 '17 at 12:24

Community

answered Mar 13 '13 at 05:12

karthick

3 Answers3