Will my upload become a YouTube Short? Check the probe first

Your file is a Short if it is square or vertical and no longer than three minutes. YouTube's three-minute Shorts page says videos with a square or vertical aspect ratio up to three minutes are categorized as Shorts for uploads after October 15, 2024, and that a wider ratio such as 16:9 keeps a video out of the Shorts feed (read 2026-10-07). Sume's video-inspect probe gives you width, height, rotation, and duration_seconds to test that.

Rotation matters: a phone clip stored sideways with a rotation flag reports its stored size, so the displayed shape is the swapped one.

The rule, as the page states it

From YouTube's three-minute Shorts page and Shorts help.

A classifier for the probe

The function swaps width and height when the probe's rotation is 90 or 270 (or -90), then tests the two conditions. The cases below are made up. One caution: the page says up to three minutes, but a margin is wise, so the second case at 180.4 seconds is flagged.

def is_short(probe):
    w, h = probe["width"], probe["height"]
    if probe.get("rotation") in (90, 270, -90):
        w, h = h, w
    return w <= h and probe["duration_seconds"] <= 180


cases = [
    {"width": 1080, "height": 1920, "rotation": 0, "duration_seconds": 58.0},
    {"width": 1080, "height": 1920, "rotation": 0, "duration_seconds": 180.4},
    {"width": 1920, "height": 1080, "rotation": 0, "duration_seconds": 45.0},
    {"width": 1920, "height": 1080, "rotation": 90, "duration_seconds": 45.0},
]
for c in cases:
    print(c["width"], c["height"], c["rotation"], c["duration_seconds"], "->", is_short(c))

Probe, then decide

Run video inspect with frames: false and feed probe to the function. If you want a long-form 16:9 video that stays out of the Shorts feed, render it wide: Timeline 1.0 accepts output.width and output.height as even integers from 256 to 2160, so 1920x1080 is available. Its default is 1080x1920, which is vertical.

The checker mirrors the page; it cannot see YouTube's side, so treat a pass as expected, not guaranteed.

Edge cases

A perfectly square 1080x1080 file passes the width-not-above-height test, matching the page's "square or vertical". A 1081x1080 file would fail, which is why exports should come from a template with exact even sizes rather than a manual crop.

The page also names dates: uploads after October 15, 2024 for standard channels. Anything older keeps its older classification, so this check is for new uploads. A probe cannot tell you the upload date, so keep that in your head, not in the script.