Why do CDN web addresses not specify protocol?

Asked

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11

Usually web addresses start with http:// or https://, but CDN addresses like jQuery and Bootstrap start with //.

Example:

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">

and

<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>

What does that mean?

http cdn

1 answer

12


This indicates the browser to use the same protocol in the address bar of the page making the request.

Does that mean that:

  • if you are on a page served via HTTP, the request will be made to HTTP CDN

  • if you are on a page served through HTTPS, the request will be made to CDN HTTPS

Example

Suppose I have a website on www.meusite.com.br, and in it I place a reference equal to the one you indicated:

<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>

On IIS, I configure to allow my page to be served by both HTTP and HTTPS.

When the user accesses http://www.meusite.com.br, the browser will fetch javascript in http://code.jquery.com/jquery-1.11.0.min.js.

When the user accesses https://www.meusite.com.br, the browser will fetch javascript in https://code.jquery.com/jquery-1.11.0.min.js.

  • 8

    That is, this has nothing to do with CDN, you can use the same technique on any responsive site both at http and https.

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