Kling 3 aspect ratios on Sume: 16:9, 9:16 and 1:1 only

kling-3 on Sume takes three aspect ratios: 16:9, 9:16 and 1:1. A request for 4:3, 3:4 or 21:9 is outside its advertised list and comes back as a 400 unsupported_capability. If you need one of those shapes, call seedance-2.5, wan-3.0 or a MiniMax H3 id, which list them.

It is the narrowest ratio list among the main video ids, so check it before you build a template around Kling.

Who takes which ratio

The ratio lists come from each model's capabilities in the Sume catalog. auto and adaptive appear on some rows and mean the model picks the frame from your input.

If you are stuck with Kling

Suppose your pipeline settled on Kling for the look of its output but you need a 4:5 or 3:4 feed format. Generate at 9:16 or 1:1 and crop afterward with a render step, keeping the subject centered in your prompt so the crop does not cut it off. That costs you some pixels. Alternatively, run the same prompt on an id that supports the ratio natively and compare the two.

Do not send a ratio Kling does not list and hope for a nearest match. The API fails closed on values outside the advertised list, which protects you from paying for a frame you did not ask for.

Check at submit time

GET /v1/videos/models returns supported_aspect_ratios for each model. A one-line check in your own code against that list turns a 400 into a message you can show your user before the call.

Where each ratio fits

A quick map from format to ratio keeps template work short.

A ratio table in your own code, filled from the catalog, also gives you a clean fallback: if a template asks Kling for a ratio it lacks, route that template to an id that lists it.

Square 1:1 is the one ratio that Kling shares with the widest set of ids, which makes it the easiest format to move between models during a comparison.

• Landscape video and most websites: 16:9.
• Reels, Shorts and TikTok: 9:16.
• Square feeds: 1:1.
• Tablet, 3:4 and ultrawide frames: use another id.