Why do the links start with //?

Question

I am wondering why some starts with "//"? Is it a shortcode for "http://"? E.g On the HTML5 boilerplate, I see the inclusion of the jQuery library as follows:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"></script>

Can I use // instead of http:// on any sites or do I need to pay for this service extra?

possible duplicate of [Two forward slashes in a url/src/href attribute](http://stackoverflow.com/questions/9646407/two-forward-slashes-in-a-url-src-href-attribute) — Quentin, Sep 11 '13 at 15:50

score 1 · Accepted Answer · edited May 23 '17 at 12:22

1

Starting with // means you keep the protocol.
If you are serving pages both as http and https this is handy as to not change the protocol when linking.
Read more at https://stackoverflow.com/a/9646435/521554

edited May 23 '17 at 12:22

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answered Sep 11 '13 at 15:50

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Why do the links start with //?

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