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.
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.
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