Shorts up to 3 minutes: the rule starts with uploads from Oct 15, 2024

Do not assume a three-minute vertical file is a Short everywhere. The YouTube help page says creators "can now create YouTube Shorts up to three minutes in length" and that videos "uploaded on or after October 15, 2024" with the proper dimensions are categorized as Shorts automatically.

What decides classification

Why this matters to a render

With Timeline 1.0, you control both dimensions and length. A 170-second 1080 by 1920 render meets the length and aspect criteria. A 190-second render does not, whatever the ratio, because it is over three minutes.

Guard in code

A cheap check before you upload: the planned duration and the output size.

def short_ok(duration_s: float, width: int, height: int) -> bool:
    return duration_s <= 180 and width <= height


print(short_ok(170, 1080, 1920))
print(short_ok(190, 1080, 1920))
print(short_ok(60, 1920, 1080))