Facebook Reels ad specs: 9:16, 1440x2560, H.264 and safe zones

Meta's ads guide for Facebook Reels asks for 9:16 video at 1440x2560, as MP4, MOV or GIF, up to 4 GB, encoded H.264 with a fixed frame rate and stereo AAC at 128 kbps or higher. Keep the top 14%, bottom 35% and sides 6% clear of key content.

Sume can produce 9:16 video, and Timeline renders 1080x1920 by default, but it cannot produce 1440x2560, because its Timeline output edge is capped at 2160. Details below, read 2026-09-29.

What does Meta list for Facebook Reels ads?

Values are from the Facebook Reels page of Meta's ads guide. The guide also says the video should have no edit lists, and limits primary text to 40 characters and headline to 55.

How close can I get with Sume?

Ask for aspect_ratio: "9:16" when you generate. Each model advertises the ratios it accepts in supported_aspect_ratios, so check the catalog before you request 9:16. Resolution tiers vary by model; gemini-omni-flash-1.1 lists 360p to 4K in 16:9 or 9:16.

For the final file, Timeline 1.0 outputs MP4 with output.width and height as even integers from 256 to 2160, so 1440x2560 is out of range. A 1080x1920 render is the default. Sume does not list bitrate, codec or loudness controls on its video endpoints, so check those against the platform page after rendering.

curl -X POST https://api.sume.com/v1/videos \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: fb-reels-001" \
  -d '{
    "model": "seedance-2.5",
    "prompt": "A barista pours latte art, close-up, slow push-in",
    "duration": 10,
    "resolution": "1080p",
    "aspect_ratio": "9:16"
  }'

How do I respect the safe zone?

Put the subject in the middle band of the frame and say so in the prompt. When you add captions with POST /v1/video-captions, use the design overrides (for example placement.anchor_ratio) to lift text above the bottom 35%.

Timeline's fit option (cover, contain, stretch, blur) decides how a 16:9 source fills a 9:16 frame; cover is the default.

What are the limits of this answer?

Sume does not offer H.264 profile, frame-rate mode or audio bitrate settings, and it cannot render 1440x2560. Whether Meta accepts a 1080x1920 ad is Meta's decision; check the page and Ads Manager.