What is Thumb-Stop Ratio?

Thumb-stop ratio is the share of people who stop scrolling and watch the first moments of your video ad — commonly measured as 3-second video views divided by impressions. It grades your hook in isolation.

Formula: Thumb-Stop Ratio = (3-Second Video Views / Impressions) x 100

Why it matters

In feed environments the first second decides everything: if the opening frame and motion don't interrupt the scroll, nothing else in the ad ever gets seen. Thumb-stop ratio isolates that moment, letting you diagnose whether a weak ad failed at the hook or later in the pitch. Paired with hold rate (how many keep watching past the hook), it maps exactly where the video loses people.

Reading the signals

• Good: thumb-stop clearly above your account's norm, with hold rate showing viewers stay past the hook
• Bad: strong thumb-stop but weak CTR — the hook grabs attention the body fails to convert
• Bad: low thumb-stop across all variants of a concept — the opening visual, not the offer, is the problem

What to do about it

Because the hook is a discrete, swappable component, the winning move is testing many openings on the same body — a numbers game that favors volume. Generating hook variations inside Claude with Polaris makes it practical to run a dozen different first-three-seconds against each other cheaply. See the full ecommerce ads glossary, or put it into practice with the Polaris AI UGC ad generator.