Three-second video views divided by impressions - the share of people your opening stopped mid-scroll. The first three seconds decide whether an ad gets watched at all, so hook rate isolates the single most important module of the creative: the open. That precision is the point. A weak ad with a strong hook rate has a narrative problem; a weak ad with a weak hook rate needs a new opening, not a reshoot. Track it per hook type, not just per ad, and note that platforms define the metric differently - fix your denominators before you benchmark anything.
Benchmark. 25%+ is strong, 15-24% is acceptable, and below 15% means the hook is not working - fix the opening. Track it weekly on every video ad; it is the first number to read when a creative underperforms.