Meta ads on phones taller than 9:16: zoom or black bars, plan for both

Meta says that on devices with screens taller than 9:16 it may either zoom your creative to fill the screen, which can crop what sits outside the safe zone, or show the 9:16 frame on a black background. You do not control which one happens, so make the 1080x1920 file survive both.

The two behaviors, from Meta's own page

Meta's safe-zone help page lists both outcomes in one bullet and then gives one instruction: keep critical text and visuals comfortably within the safe zone to protect key elements in both cases. For 9:16 ads in Stories, Reels, Feed and Facebook in-stream reels, it asks you to keep the top, bottom and sides free of key creative elements, text and logos.

The page also notes that 9:16 video ads in Instagram Feed use the same safe-zone guidance as Reels and Stories, and that Ads Manager has a Safe zone guardrail toggle that draws a yellow overlay on your creative.

Why zoom is the case that bites

A zoom to fill a taller screen is a crop. Take a 9:20 phone showing a 9:16 clip. To fill the screen height, the player scales the clip until its height matches, and the clip is then wider than the screen, so the sides are cut. The fraction of the width that stays is (9/20) / (9/16) = 16/20 = 0.80, so 10% is lost on each side.

That is an illustration of the mechanism, using a hypothetical 9:20 screen, not a figure from Meta. Meta does not publish how much it crops. What the arithmetic shows is that text placed at the very left or right edge is the first thing to go, which matches Meta's rule about keeping the sides free.

A build that survives both

Use the inner part of the frame for anything that must be read. With the 9:20 example, a margin of 10% each side is the minimum, so a 1080-wide frame keeps text between x = 108 and x = 972. Add the top and bottom margins that the Reels safe zone needs on top of that, and keep your logo inside the same box.

In Sume, the Timeline default output is already 1080x1920. Caption jobs accept a design.typography.safe_width_ratio field, which is the width the text may use. A value of 0.80 matches the 10% side margins above. Confirm the documented range in the caption docs before relying on a value.

Test the zoom case for free

To see the zoom crop on your own clip, ask the video filter check endpoint to validate a crop that keeps 80% of the width. The check is free, creates no job and reserves nothing, and it returns diagnostics instead of a 400. The real encode costs $0.02 per job, so look at the crop on a still first and only then pay.

Run the crop encode on a copy, pull a still with video inspect, and see whether anything important was cut. Then move the offending element inward and re-render.

curl -X POST https://api.sume.com/v1/video-filter/check \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/talk.mp4",
    "ops": [{ "op": "crop", "x": 0.1, "y": 0, "width": 0.8, "height": 1 }]
  }'

A checklist before you upload

Run the Safe zone guardrail in Ads Manager as the last step, because it is Meta's own view of the safe area. Use it to confirm that the Sume output, with its burned-in captions, keeps every key element inside the yellow overlay.

• Output is 1080x1920 and 9:16 exactly.
• Text and logo sit inside about 10% side margins.
• Nothing key sits in the top or bottom edge bands.
• The crop preview of 80% width still reads.