Guide
9:16, 4:5, or 1:1? The honest answer is "it depends on the placement" — but there's a clear default for each, and one rule that matters more than the ratio you pick.
9:16 (full vertical) is the native format for full-screen placements: TikTok, Instagram Reels, and YouTube Shorts. It fills the whole screen, which is exactly the immersive feel those surfaces reward. 4:5 (portrait) is the workhorse for the Facebook and Instagram feed — it occupies more vertical space than a square without being cropped in-feed, so it's the safest single ratio when one asset has to cover feed delivery. 1:1 (square) is the conservative, universally compatible option that rarely wins but rarely breaks — useful for older placements and some partner inventory. If you can only ship one ratio for short-form, ship 9:16; if you can only ship one for the Facebook and Instagram feed, ship 4:5.
Every full-screen placement overlays UI on top of your video — the caption, the profile icon, the like and share buttons, the CTA bar. Those elements live along the bottom and right edges. If your hook text or your product sits under that UI, it's effectively invisible no matter how good the ratio is. Keep the critical 10 to 15 percent of each edge clear and center your key message. Picking 9:16 and then burying your hook behind the caption is the most common framing mistake — and it's entirely preventable. The same safe-zone rule governs your text overlay on video ads, since on-screen words land in exactly the area the platform UI likes to cover — the broader version of this discipline is mobile-first ad design. And because each surface hides different regions behind different chrome, the ratio decision is really a per-placement decision — testing ad creative across placements covers how to check the cut you actually ship to each one.
When budget allows, yes — shoot or frame so the same edit exports cleanly to 9:16 and 4:5, and let each placement serve its native size. The cheap version of this is composing your shots with headroom so a center crop survives. What you should avoid is uploading a single 1:1 asset everywhere and letting the platform letterbox or crop it unpredictably; that's how a strong hook ends up pillarboxed in the middle of a full-screen feed. The format trade-offs sit alongside the length question and the static vs video decision — all packaging choices around the same core creative.
The right aspect ratio gives strong creative room to breathe; it can't save a weak hook. Once your framing and safe zones are set, the question that actually moves results is whether the content holds attention — and you can check that before you pay for reach. PreTestAds predicts engagement from the creative itself, so you can confirm your hook reads inside the safe zone and your CTA lands while people are still watching. The full approach is in ad creative analysis, and reading the result is covered in how to read an attention curve. Pre-testing screens the creative; live A/B testing confirms the winner.
Upload your video ad and see how it holds attention — first analysis free, no credit card.
Test Your Video AdFor full-screen placements like TikTok, Reels, and Shorts, 9:16 vertical is best because it fills the entire screen. For mixed feed and Stories delivery on Facebook and Instagram, 4:5 is the safest single ratio — it takes up more vertical space than 1:1 without getting cropped in feed.
If one creative has to run across feed, Stories, and Reels, 4:5 is the practical default for feed-weighted delivery, while 9:16 is built for full-screen Stories and Reels. Many advertisers upload both and let placement-specific assets serve where each fits.
Yes, indirectly. The right ratio gives you more screen real estate and prevents awkward cropping that buries your hook or CTA. But ratio is a packaging decision — it amplifies strong creative and can't rescue a weak hook. Get the framing right, then test the content inside it.