Square vs Vertical Video Ads: Which Format to Use
A direct comparison of square and vertical video ad formats and when each one fits.
Vertical (9:16) is the safer default for most modern placements — Reels, Stories, TikTok, and Shorts are all full-screen vertical, and a vertical video fills that space naturally. Square (1:1) still has a place in older feed placements and some carousel or catalog formats, but it's the exception now rather than the standard. The real answer is to match the format to the placement, then test creative within that format rather than debating the ratio in the abstract.
Why has vertical become the default?
Phones are held vertically, and the placements that get the most inventory today — Reels, Stories, TikTok's main feed, YouTube Shorts — are all full-screen vertical experiences. A vertical video takes up the entire screen with no dead space above or below it, which means nothing else competes for the viewer's attention. That's a structural advantage independent of the actual creative.
Where does square still make sense?
Square can still work in classic feed placements where the surrounding UI (other posts, sidebars) means a video was never going to be full-screen anyway, and in some cross-platform buys where one asset needs to sit reasonably well in both feed and profile-grid contexts. If you're running the same campaign across a mix of older and newer placements, a square cut can act as a safer middle ground than sending vertical into a square slot and having it letterboxed.
What actually matters more than the ratio?
Regardless of aspect ratio, keep the hook in the very first frame, keep key subjects and text inside the safe zones so platform UI (captions, buttons, profile info) doesn't cover them, and make sure the video reads clearly even with sound off. Those three things affect performance more than whether the frame is square or vertical. A well-shot vertical ad with a weak hook will still lose to a mediocre one that nails the opening second.
Should you produce both formats for every campaign?
If budget and time allow, yes — but the honest constraint most teams have isn't knowing which ratio to prioritize, it's the cost and time of producing multiple cuts of the same creative. Polaris addresses that by generating UGC-style video ads directly inside a Claude chat: you attach a product photo or paste a script, ask for the ad in whatever settings you need, and a live panel renders it in the conversation, typically in under three minutes. Because renders run in parallel batches with ZIP download, producing a vertical and a square cut of the same concept doesn't require a second production cycle, just a second request.
How do you know which format actually won?
Whichever ratio you run, the same metrics decide the outcome: hook rate tells you if the opening frame is doing its job, and ROAS tells you if the format translated into results worth the spend. Use a hook generator to make sure the opening line or visual works in whichever frame you choose, and check outcomes with a ROAS calculator before scaling either format further.