4K vertical Short in Timeline: the 2160 cap and 1214x2160

Sume Timeline accepts output.width and output.height as even integers from 256 to 2160. A 2160x3840 vertical frame is outside that range and is refused. The largest 9:16 frame under the cap is 2160 tall by 1215 wide, and 1215 is odd, so the nearest valid frame is 1214x2160 (about 0.562, versus 0.5625 for exact 9:16). Read from the Timeline docs on 2026-10-06.

Do I need more than 1080x1920?

For Shorts, YouTube's page asks for square or vertical and up to three minutes, and does not require 4K. Most viewing is on phones, where 1080x1920 is the default Timeline frame. Choose 1214x2160 only when a downstream step crops or zooms into the frame.

How do I pick the frame size?

How do I check before paying?

The unbilled plan call validates the schema and the compile without creating a job, so a bad size fails there for free.