How do you separate a bad ad from a bad landing page?

[SophieR]

If an ad gets clicks but few conversions, how do you decide whether the problem is the promise in the ad, the audience, or the landing page? Which numbers or tests help you isolate the weak point without changing everything at once?

 

[eHarper]

The quickest way to isolate it is to hold one side constant. Keep the landing page the same and run two ads with different promises; if conversions don't move, the page or offer is the weak link. Then flip it - same ad, two landing pages. I also check message match: if the headline doesn't restate the ad's promise, you lose people in the first five seconds no matter how good the page is. CTR describes the ad, conversion rate describes the page, and the gap between them points at the culprit.