4:5 or 9:16 for video ads: what each platform's page lists

Use 9:16 for full-screen placements (TikTok, Instagram Reels, Pinterest) and 4:5 only where the platform's page lists it: LinkedIn (720x900, its recommended vertical ratio) and Pinterest. LinkedIn also lists 9:16 at 720x1280. The pages read on 2026-09-29 do not agree on one shape, and Sume video models offer 9:16 but not 4:5.

What does each page list?

Only ratios named on the platforms' own pages are shown.

How do I get 4:5 with Sume?

No Sume video model lists 4:5; 9:16 is listed on every model that lists aspect ratios (grok-imagine-video-1.5 lists none). Two routes: crop a 9:16 or 1:1 clip with POST /v1/video-filter (a crop op with fractional x, y, width, height; keeping the full width and 70% of the height of a 9:16 frame gives about 0.80, which is close to 4:5), or render a Timeline with output of 1080x1350, where fit decides cover, contain or blur.

curl -X POST https://api.sume.com/v1/video-filter \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: crop-45-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/vertical.mp4",
    "ops": [{ "op": "crop", "x": 0, "y": 0.15, "width": 1, "height": 0.7 }]
  }'

Which should I pick?

Follow the placement: if a page lists only 9:16 for full-screen, use 9:16. Where both are listed, pick per creative, and keep key content in the center band so both crops work. Sume's video-filter check route (/v1/video-filter/check) is free if you want to preflight a crop.

What are the limits of this answer?

The crop is plain geometry, not a Sume ratio feature, and lands near 4:5 rather than exactly on it. For an exact 4:5 use a Timeline output of 1080x1350. Platform pages can change; re-read them before you deliver.