Final answer:
The recommended parameter for identifying different versions of an ad is 'utm_content'. UTM parameters are tags added to the end of a URL that track different aspects of a user's interaction with the ad.
Step-by-step explanation:
The recommended parameter for identifying different versions of an ad is utm_content.
UTM parameters are tags added to the end of a URL that track different aspects of a user's interaction with the ad. The utm_content parameter is used to differentiate the content or message within an ad. It can be used to track different versions, such as different headlines or images, and analyze their performance.
For example, if a company is running two versions of an ad with different headlines, they can use the utm_content parameter to differentiate between them and analyze which version performs better in terms of clicks or conversions.