Twitch vertical clips: crop an older 16:9 clip to 9:16

To cut a vertical 9:16 slice from a horizontal 16:9 clip, send a crop op to Sume's POST /v1/video-filter with width 0.316, height 1 and x 0.342 for a centered slice. Crop values are fractions of the frame, so the same numbers work at any source resolution.

Twitch details are from its 2026-06-17 Dual Format post, and crop rules from Video filter, read 2026-09-30.

What did Twitch change about vertical clips?

The post says Dual Format lets streamers stream horizontal and vertical at the same time, and that streamers get both a horizontal and a vertical version of their Clips and VODs. The post does not say it adds vertical versions to clips made earlier, so for those you may need to make the vertical cut yourself.

What are the crop numbers for 9:16?

A 9:16 slice of a 16:9 frame is as tall as the frame and 9/16 divided by 16/9 wide, about 0.316 of the width. That is arithmetic, not a Sume or Twitch claim.

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/clip.mp4",
    "ops": [{ "op": "crop", "x": 0.342, "y": 0, "width": 0.316, "height": 1 }]
  }'

How do I run it?

Import the clip with POST /v1/media-imports first, because the filter only reads media.sume.com files. The /check route above is free and returns diagnostics without creating a job. When it says valid, send the same body to POST /v1/video-filter with an Idempotency-Key. The source must be 300 seconds or shorter; trim longer recordings first with Video trim.

Does a centered slice always work?

No. A fixed slice cuts off whatever sits at the sides, such as a facecam in a corner. Move x to follow the subject: any value from 0 to 0.684 keeps the slice inside the frame. See crop video without losing quality for how the crop behaves on the pixels.