YouTube Shorts max resolution is 1080p: skip the 4K upscale

Do not upscale a Short to 4K: YouTube's Shorts help page says you can upload Short videos with a maximum resolution of 1080p, and that Shorts can be up to 3 minutes long with the multi-segment camera. The useful upscale is the one that gets a smaller clip up to 1080 x 1920. With Sume that is a scale_ratio of 1.5 on a 720 x 1280 source.

The YouTube statements come from Get started creating YouTube Shorts, read 2026-10-02. That page does not spell out aspect ratio numbers, so the 9:16 shape here is the common vertical format, not a quote.

What does YouTube say about Short resolution?

Two sentences matter. Shorts can be up to 3 minutes long with the multi-segment camera, and you can upload Short videos with a maximum resolution of 1080p. That is the ceiling on the page I read; a 4K file does not buy more sharpness for a Short, it only enlarges the upload.

What ratio takes a small clip to 1080 x 1920?

Sume's video upscale takes a scale between 1.1 and 4. The target is 1080 pixels wide, so divide it by the source width. The table shows the common cases; all of them stay inside the range, and the result should be checked, since the docs do not state exact output dimensions for each ratio.

What are the limits on the Sume side?

Video upscale takes at most 30 seconds per call, priced per input second, and the default reservation when you omit duration_seconds is 5 seconds. A Short can run 3 minutes, so a full-length Short needs splitting into pieces of 30 seconds or less, or leaving at native resolution. For the cut, use video trim; for stitching back, Timeline 1.0, whose default output is 1080 x 1920.

curl -X POST https://api.sume.com/v1/video-upscale-1.0/upscale \
  -H "Authorization: Bearer $SUME_API_KEY" -H "Content-Type: application/json" \
  -H "Idempotency-Key: short-up-001" \
  -d '{"video_url":"https://media.sume.com/artifacts/artf_demo/short720.mp4",
       "scale_ratio":1.5,"enhancement_tier":"standard","duration_seconds":20}'

Is 1080 x 1920 really the target?

On the page I read, the stated cap is 1080p, and 1080 x 1920 is the portrait form of it. Other sizes, such as 720 x 1280, are common and fine to upload; the point of the upscale is not to meet a minimum but to avoid soft footage when a platform scales it up on a large phone screen. If your source is a generated clip that came out at 720p, a 1.5x upscale gives a 1080-wide master.

For a clip that is the wrong shape, not too small, the order matters. Crop to 9:16 first with video filter, then trim and conform with video trim (a conform with both sides set stretches the frame, so only do it once the ratio is already right), and only then decide whether the result needs an upscale. Each step is a separate job and each output is a new MP4, so you can stop at any point and keep the previous file.

Finally, keep the master. If YouTube changes its Shorts limits, a clean 1080 x 1920 file and the original are both still on hand, and you can re-cut without re-running the whole chain.

When is upscaling the wrong move?

The rule is short. Match 1080 x 1920, keep clips under three minutes, and spend the upscale only where the source is smaller than that.

• The clip is already 1080p: you only add cost and time.
• The clip is a screen recording with small text: upscaling invents detail and can smear letters; re-export from the source instead.
• The clip needs a different shape, not more pixels: crop first with video filter, then trim to size.