Google AdSense has officially approved Responsive Design and what that means is you can serve Google ads of varying dimensions corresponding to the viewport size (screen resolution) of the visitor’s device.

For instance, if a visitor is reading your web page on desktop, you can choose to serve the large 728×90 (leaderboard) unit but if another visitor is viewing the same web page on a mobile phone, you can display the smaller 468x60 ad unit. The AdSense code detects the size of the visitor’s screen and serves the appropriate ad unit that will best fit the available space.

You can serve responsive Google AdSense ads in both synchronous as well as asynchronous (non-blocking) fashion. The latter is a more efficient and recommended method as the JavaScript ad code loads in parallel and therefore does not block the other elements of the web page from rendering. In other words, your pages will load faster improving user experience.

How to Generate Responsive AdSense Ads

Open your AdSense dashboard and under My Ads, click “Create new ad unit.” Set Ad Size as “Responsive Ad Unit” and click the “Save and Get Code” button to generate the JavaScript code for your Responsive AdSense ad. The default code is something like this:

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<ins class="adsbygoogle"
     style="display:block"
     data-ad-client="ca-pub-12345"
     data-ad-slot="xxxxx"
     data-ad-format="auto"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>

AdSense computes the available width and renders the largest ad that will fit that space. This may not always be the most appropriate approach since the best performing ads are rectangles and skyscrapers and not necessarily the leaderboards.

There is however an option to force the ad unit to always serve the rectangle or the skyscraper. You can change the value of the data-ad-format variable in the JavaScript code from “auto” to “rectangle” and it will always serve one of the rectangular formats. Similarly, you can set data-ad-format to “vertical” to always render a 120x600 or 160x600 rectangle. The modified ad code would be:

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<ins class="adsbygoogle"
     style="display:block"
     data-ad-client="ca-pub-12345"
     data-ad-slot="xxxxx"
     data-ad-format="rectangle"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>

Responsive AdSense Ads (Another Approach)

Whether you set data-ad-format as “auto” or “vertical” or “horizontal” or vertical, the Google AdSense algorithms will still decide which ad to serve. For instance, if you ask for an rectangle, you may either get a medium rectangle or a large rectangle.

SHould you wish to force AdSense to serve ads of a particular size while staying responsive, you can consider custom-sized ads. The size of these ads is determined based on the screen but the publisher has more control over the banner size that is served.

<div id="google-ads-1"></div>

<script type="text/javascript">

    /* Calculate the width of available ad space */
    ad = document.getElementById('google-ads-1');

    if (ad.getBoundingClientRect().width) {
        adWidth = ad.getBoundingClientRect().width; // for modern browsers
    } else {
        adWidth = ad.offsetWidth; // for old IE
    }

    /* Replace ca-pub-XXX with your AdSense Publisher ID */
    google_ad_client = "ca-pub-XXX";

    /* Replace 1234567890 with the AdSense Ad Slot ID */
    google_ad_slot = "1234567890";

    /* Do not change anything after this line */
    if ( adWidth >= 728 )
      google_ad_size = ["728", "90"];  /* Leaderboard 728x90 */
    else if ( adWidth >= 468 )
      google_ad_size = ["468", "60"];  /* Banner (468 x 60) */
    else if ( adWidth >= 336 )
      google_ad_size = ["336", "280"]; /* Large Rectangle (336 x 280) */
    else if ( adWidth >= 300 )
      google_ad_size = ["300", "250"]; /* Medium Rectangle (300 x 250) */
    else if ( adWidth >= 250 )
      google_ad_size = ["250", "250"]; /* Square (250 x 250) */
    else if ( adWidth >= 200 )
      google_ad_size = ["200", "200"]; /* Small Square (200 x 200) */
    else if ( adWidth >= 180 )
      google_ad_size = ["180", "150"]; /* Small Rectangle (180 x 150) */
    else
      google_ad_size = ["125", "125"]; /* Button (125 x 125) */

    document.write (
     '<ins class="adsbygoogle" style="display:inline-block;width:'
      + google_ad_size[0] + 'px;height:'
      + google_ad_size[1] + 'px" data-ad-client="'
      + google_ad_client + '" data-ad-slot="'
      + google_ad_slot + '"></ins>'
    );

    (adsbygoogle = window.adsbygoogle || []).push({});

</script>

<script async src="http://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js">
</script>

Go to your AdSense dashboard and either create a new ad unit or use one of your existing ad units. Make a note of the ID of your ad unit and also your AdSense Publisher ID and paste these values in Line #15 and #18.

Next, copy-paste the above snippet anywhere on your web page and, based on the size of the user’s device, the most appropriate AdSense Ad will be served. If you wish to include multiple responsive AdSense ad units on the same web page, just use the same snippet of code but increment the DIV ID in lines #1 & #6 such that they become google-ads-1, google-ads-2 and so on.