An innovation Google introduced to PPC advertising came a few years ago with responsive adverts, for both publishers and advertisers. Responsive search adverts consist of the ability to change the headline/description to suit the web user viewing the search ad, whereas responsiveness for publishers could be defined as adverts that change the size, responsively, based on the available space around them. Based on this, if the allocated space was 300×250 pixels, such a size advert could appear there. If 336×280 pixels are free, the ad unit shown will be bigger (and so on).
Responsive adverts have both pros and cons associated to using the, highlighted below.
 

Pros of Responsive Adverts

• Better performance – Since responsive adverts fit to the size allocated to them, the majority of the times that adverts appear will be as large as possible, based on the size that the unit takes up. In general, the larger the advert, the more exposure it will get and the higher the CTR. With responsive adverts always at the upper limit of adverts showing, the performance should be better than a fixed unit size.
• Less code required – If you want to test the size of different adverts to see how it fairs against other sizes, this would require lots of code to do. Responsive adverts have multiple types of ad unit sizes, all in one piece of simple coding.
• Less effort/testing required – As mentioned above, manually testing what ad unit size works best for your website is a timely process, where results are not guaranteed. With responsive adverts, the adverts are auto-optimized based on the theme, design and space available so you do not need to do this yourself.

Cons of Responsive Adverts

• No control of ad sizes – As much as it is a good thing that responsive adverts fill the space available, it can also be seen as a bad thing. This is because it might not always be in the best interest, both in terms of ad performance or the web user’s experience, to have larger adverts. Also, the choice of shape (rectangle, as opposed to square), will have an impact to the ad performance.
• Not guaranteed results – As much as it is likely that the ad performance will increase with responsive adverts, it is not by any means guaranteed. Therefore, it needs to be taken with a pinch of salt whether responsive adverts will work in different areas of your website or not.
• Aesthetically not always the right choice – Choosing the largest size advert will not always give the best user experience, especially if it takes up lots of room and reduces the exposure level of the content accordingly. Adverts are meant to complement the content: not overtake it. With responsive adverts, it is sometimes difficult to stop this from happening.