Google
Google now lets advertisers create and track custom metrics at keyword and ad levels through Custom Columns in AdWords, adding to the campaign and ad group levels. It can help marketers gain additional insights into how their campaigns perform based on non-standard metric targets. For example, per Google, advertisers can see how engaging ads are on mobile device by creating a custom column for mobile click-through rate (CTR). They also can see how specific keywords convert by creating a custom column for mobile conversion rates.