Official Artist Channel Shorts rule starts Dec 8, 2025: trim to 3:00

On an Official Artist Channel, a video that is square or vertical and up to three minutes long is categorized as a Short only if it was uploaded on or after December 8, 2025. Earlier uploads stay long-form. Standard channels use October 15, 2024 as their cutoff. If you cut music-video snippets for an artist channel, trim each to 3:00 or less, keep the frame square or vertical, and check both before you upload. Sume's video trim does the cut; video inspect reads the result.

What YouTube's help page says

YouTube Help: Understand three-minute YouTube Shorts, read 2026-10-04, sets one rule with two start dates. The rule is the same on every channel: a video counts as a Short when it is square or vertical and no longer than three minutes. Wider formats such as 16:9 remain long-form videos. Only the date from which the rule applies differs, and it depends on the channel type.

The upload page, Upload YouTube Shorts, repeats the same two conditions: up to 3 minutes, and a square or vertical aspect ratio.

Cutting the clip to 3:00 with Sume

Video trim takes one clip already on media.sume.com, a start, and exactly one of end or duration, and returns a new MP4. The output window is 0.2 to 900 seconds, so a 2:55 snippet from a longer concert film is a single call. The default precision is exact, a frame-accurate re-encode; keyframe is a stream copy whose cut may start a GOP early, and the result reports actual_start_seconds so you can re-base.

Import the source first with POST /v1/media-imports; trim refuses off-host URLs. A trim is a flat **$0.02 per job** in the docs (confirm in GET /v1/catalog), with no model inference.

curl -X POST https://api.sume.com/v1/video-trim \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: artist-clip-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/concert.mp4",
    "start": 62,
    "duration": 175,
    "mode": "sync"
  }'

Getting the frame square or vertical

Trim keeps the source geometry unless you pass output, so a 16:9 concert film stays 16:9 and would remain long-form. The Timeline 1.0 render defaults to 1080x1920, takes output.width and output.height as even integers from 256 to 2160, and fits each slot with fit: cover (default), contain, stretch or blur. For a square Short, set 1080x1080. Feed the trimmed MP4 in as a video[] slot, with the original audio as the spine, or use audio.mode: "silence" if the clip is picture-only.

Check before you upload

Run video inspect on the finished file. The probe object carries duration_seconds, width, height and rotation. Your gate is: duration at most 180 s, and width less than or equal to height after you account for rotation. With frames: false you get the probe without stills.

What Sume does not do: it does not upload to YouTube, set the channel type, or decide how YouTube categorizes the file. The categorization happens on YouTube's side from the length and dimensions you ship. The jobs and results page covers polling if you run trim in the default async mode.