X video 720x1280 portrait and 1080p playback: conform with trim

X recommends 1280x720 for landscape, 720x1280 for portrait and 720x720 for square. Subscribed users can upload 1080p and get 1080p playback; unsubscribed users get 720p playback. On Sume, video-trim can conform width and height anywhere from 256 to 2160, so both a 720p and a 1080p export are possible.

X facts are from its Media best practices page, read 2026-10-01. Sume facts are from Video trim, Video 1.0 and Video Router.

What sizes does X recommend?

X marks these as recommended, not required. The same page also lists a dimensions rule of 32x32 to 1280x1024, which a 1920x1080 file would exceed, so test a 1080p upload before relying on it.

How do I set the size on Sume?

video-trim takes output: { width, height, fps } with exact precision. Width and height are 256 to 2160, and fps is 24, 25, 30 or 60. The docs do not say how a size with a different aspect ratio than the source is handled, so choose an output with the same ratio as your clip.

What ratios can I generate in the first place?

Video 1.0 lists aspect_ratio values 21:9, 16:9, 4:3, 1:1, 3:4 and 9:16, with resolution of 720p (default) or 1080p. Gemini Omni Flash 1.1 on Video Router is 3 to 10 seconds at 360p, 720p, 1080p or 4K, 16:9 or 9:16. Generate at 9:16 for a portrait Post and 1:1 for square.

Should I export 720p or 1080p?

If your posting account is subscribed, a 1080p file can play at 1080p; if not, X plays 720p, so a 720p export avoids extra bytes. Which one your account gets is an X account matter, not something Sume can see. The size and fps rules are also in the 1280x1024 conform post.