Guide
People talk about "the hook" like it's one thing. It's two. The still that represents your ad and the first seconds of motion do different jobs, fail for different reasons, and deserve to be tested separately.
The first frame is the still that represents your ad before anyone taps play — in a paused feed, on autoplay that hasn't triggered yet, or as the thumbnail on a placement that shows one. Its only job is to make a thumb stop. The first three seconds are the opening motion that plays once the scroll pauses. Its job is to convert that half-second of attention into an actual watch. The frame wins the impression; the opening wins the watch. Miss the first and the second never happens.
First frames die from being legible but boring: a clean product-on-white shot, a logo, a title card, a face mid-blink. Nothing wrong with them — and nothing that earns a stop. A strong first frame has tension or curiosity baked into a single image: an unexpected object, a visible before-state, a face caught mid-reaction. This is the same attention problem as choosing the best thumbnail for video ads — one frame doing the work of stopping the scroll.
The opening motion fails differently. It fails from slow starts — logo animations, establishing shots, a person walking into frame before speaking, a claim that takes six words of throat-clearing to arrive. The viewer already stopped; now you're spending their patience on setup instead of payoff. This is what hook rate actually measures: the share of viewers who survive those three seconds. Openings that start mid-action, mid-sentence, or mid-result hold far more of them.
This is the trap: a great opening line wrapped in a dull first frame gets a fraction of the reach it deserves, because too few people ever start it. And a scroll-stopping frame followed by a slow open bleeds those hard-won viewers in seconds. You can't average them — both gates have to pass. The craft of writing the opening is covered in how to write a TikTok hook; the point here is that the still and the motion are separate problems and hiding a weak one behind a strong one just moves the leak.
Because they fail for different reasons, test them for different things. Screen the opening still as a static image for stopping power, and screen the first seconds of the cut as video for predicted attention. PreTestAds scores both against a benchmark of top-performing ads — so you can see whether the frame earns the stop and whether the opening holds it, before a single impression is bought. It's a pre-launch screen, not a guarantee, but it tells you which of the two gates is leaking while you can still fix it cheaply.
Upload your first frame and your opening cut, and see predicted attention in minutes — up to 8 free credits.
Test Your OpeningThe first frame is the still image that represents your ad before it plays — it decides whether someone stops scrolling at all. The first three seconds are the opening motion that decides whether they keep watching once it starts. One wins the impression, the other wins the watch.
They're sequential gates, not competitors. A weak first frame means the first three seconds never get seen; a strong first frame with a slow opening loses the viewer anyway. Both have to pass, and they fail for different reasons — so they're worth testing separately.
Screen the opening still for stopping power as a static image, and screen the first seconds of the cut for predicted attention as video. Pre-testing shows whether the frame stops the scroll and whether the opening holds it — before you pay for impressions to learn the same thing.