Click-through rate (CTR)
Short definition
Click-through rate (CTR) measures the share of people who see an advert or link and go on to click it.
CTR is calculated by dividing clicks by impressions, and shows how well a headline, advert copy or meta description captures interest. It is measured the same way in search results, display adverts and email subject lines.
A low CTR can mean the message does not match the audience, or that ranking is limiting visibility. On platforms such as Google Ads, CTR feeds into the quality score and indirectly affects cost per click.
It is often confused with conversion rate: CTR measures interest, conversion rate measures whether that interest turns into a result. A high CTR paired with low conversions usually points to a mismatch between the offer and the landing page.
Why it matters
A low CTR means most of the advertising budget is spent unseen; raising spend without fixing the message or headline only compounds the problem. Because it feeds into ranking and quality score, it works as an early warning sign.
Illustrative example
When a spa chain's search advert headline led with booking convenience instead of price, click-through rate rose noticeably on the same budget and cost per click fell. Only the headline had changed.
