Google Adsense provides a wide range of ad sizes for you to choose from, so that it can fit into almost any website design and templates. Each of these sizes can be also configured to show various different types or formats of ads as you seem fit. There are several different types of Google Adsense ad formats that you can choose from.
Some ad formats are known to perform better than others. In spite of the several different sizes of ads, you are allowed to insert only three ads (or ad slots) into each of your pages, which means you will have to choose from among these different sizes and formats. In order to choose the right size and type that best fits your requirement, you should have an understanding of what each of these sizes are and what the formats are.
Let us look at all the various Google Adsense ad formats that are available to you.
These ads have only text and an URL as the content. These are the most popular among advertisers as it usually fits pretty well with most websites including blogs. They are also easy to create for most small advertisers and has a fast approval time as the approval process is automated.
As these ads contains only text, it is very easy to customize the font, colors and the overall look and feel of the ads to better suit your website. The ads are static and non-intrusive in nature, which means it does not steal focus from your own website and website content. Also, being only text it can be morphed to display multiple ads in almost all different sizes of the ad slots.
There is only a single interaction that the viewer has with the ad, which is clicking on it and it redirects them to a predefined URL or webpage.
Image Ads or Standard Display Ads
These are graphic ads which is a static or animated image in a predefined size. These ad type takes more time and effort from the advertisers, and also require to approved by Google before it is shown in the search network. The Google approval process is not usually the fastest in the world in my experience, takes anywhere from a couple of days to weeks. Due to this reason, there are usually less graphic ads than text ads.
These are animated or static ads that can be developed in any of the technologies, including HTML, animated GIF or flash. Some of the larger ad sizes also support video ads.
Just like the text ads, these have only a single interaction. Clicking anywhere on the ads takes the user to a destination webpage.
Rich Media Ads
These are usually animated ads developed using flash which also allows the user to interact with it in many different ways. The users can expand the ads to a larger size, initiate a phone call, play videos among other things. These type of ads are much more complex to create and needs significant time and effort to make sure that all interactions works well across platforms and web browsers.
These ads provide a much richer experience for the user, but at the risk of annoying some users. Because of the complexity and effort involved, these are developed by mostly big budget advertisers.
Link Unit Ads
These are ads that display a bunch of topics that are relevant to the user or your webpage content. Clicking on any of these topics, opens a page of related ads relevant to topic that was clicked. These ads are highly relevant to the topic and hence have a high CTR. Any click on these ads on the page will directly be attributed to your website and you earn revenue from those.
These type of ads display similar to the text ads. On the flip size, it requires at least two clicks from the user for you to get any revenue.
The following two types are not necessarily an ad format but more of a method of ad delivery which is different than the much more traditional web browsing. They refer to the mobile advertising which covers web enabled devices such as the smartphones and tablets. RSS feeds is another content delivery mechanism that is widely used especially by blogs and news sites. Monetizing these channels can bring in more revenue as the mobile web usage grows exponentially across the world.
These are similar to the previous ad types but are displayed to the mobile users. These give the ability to advertisers to target mobile users differently than the desktop users. If you have a mobile version of the website, then these are ads that you want to target.
Different content networks support different ad formats in the mobile channel, but image or standard display ads are most popular. Due to the smaller screen size of phones and tablets, the number of ads that can be shown is limited which means there is more competition for less space. The CPC on these ads could get higher and higher for this reason.
If your website provides an RSS feed that is subscribed by the users then you might want to monetize your feeds separately. As feeds are delivered to user quite differently than the webpage, you will need to enable the Adsense for feeds option in your Adsense account.
As with ad slots in webpages, you can choose to show different ad types in your feeds.
Understanding all the available Google Adsense ad formats should give you an idea as to which of these formats you want to use on your website. You should also try out each of these formats separately in order to gauge as to which of them works best for your site and niche.