Ad Rotation controls what percentage of impressions each ad version receives. It is used to help test adverts (A/B testing) and ultimately control which adverts receive the most search impressions.
The end goal of ad testing is to work out what is the most effective adverts are- and make sure they receive the most impressions. Google can automatically show ads more often that have either the highest CTR or the highest conversion rate, or manual ad testing can be done.
The “% served” statistic showing how often each ad has been shown in relation to the rest of the active ads (within the same ad group.)
Automatic Ad Rotation (Testing run by Google)
This campaign setting automates ad testing by allowing Google to show the winning ad version more often. Google then automatically show ads more often that have either the highest CTR or the highest conversion rate.
- Optimise for Clicks (default setting): Allows Google to automatically show ad versions that get more click-throughs than other ads versions. This setting is useful for new accounts or campaigns to improve quality score and gather performance data. Optimising for clicks is showing the adverts with the highest CTR more often. This is useful was of improving CTR- or doing initial testing on new accounts if limited conversion data is available.
- Optimise for conversions: Automatically show advert versions more often that get the most conversions like leads or sales. This may generate fewer clicks & traffic- but more suited for direct response advertising.
The ratio of ad serving gets based on the degree the winning ad is better than the losing ad/s. When a clear winner is established- it is possible for the other advert/s to get less than 1% of the impressions. If no winner is established- the ads will serve on an equal basis.
Manual Ad Rotation
It is also possible to rotate the adverts equally- and not allow Google to show the best performing ads more often. This is for more advanced ad testing- where losing ads get paused manually. (The losing ad gets paused manually, and a replacement “experiment” ad version is created to beat the winning control ad).
- Rotate evenly: Gives equal preference to all adverts in the ad group, regardless of how each ad performs. After 90 days, the ad rotation in this ad group will automatically begin to optimise for either clicks or conversions.
- Rotate indefinitely: Shows ads in a manner similar to “Rotate evenly”, but does so for an indefinite amount of time, without ever allowing Google to automatically optimise.