Grok Imagine 21:9 and 5:2 ratios vs Sume's Grok aspect list
xAI added 21:9 and 5:2 to Grok Imagine image on Aug 28. Sume's Grok list has 20:9 and 2:1 but neither of those two, so pick a listed ratio for banners.
xAI's August 28 release notes say Grok Imagine image generation and editing now accept 21:9 (cinematic widescreen) and 5:2 (wide banners). Sume's Grok list does not include either value. Its widest entries are 20:9 and 19.5:9, so on Sume you pick one of those for a banner.
xAI's side is from its release notes; Sume's from the Grok aspect list in the API contract and the Image API docs, read 2026-10-01.
What did xAI add on August 28?
The entry lists three changes to the image API: an auto quality value that is now the default, up to 5 source images per edit request, and the two new aspect ratios. For the ratios it says generation and editing both accept them. The notes link to xAI's own Image Generation page for details, which this post does not rely on.
Which wide ratios does Sume list for Grok?
The Grok Imagine list in Sume's code is commented as the official Grok list and has no 4:5. The decimals below are plain division, shown so you can see how close the nearest listed value is.
| Ratio | Width / height | xAI notes (Aug 28) | Sume Grok list |
|---|---|---|---|
5:2 | 2.50 | Accepted | Not listed |
21:9 | 2.33 | Accepted | Not listed |
20:9 | 2.22 | Not in this entry | Listed |
2:1 | 2.00 | Not in this entry | Listed |
16:9 | 1.78 | Not in this entry | Listed |
Does Sume accept 21:9 anywhere?
Yes, for other models. The generic normalized list in the Image API docs includes 21:9 and 9:21, and says to use "auto" for provider choice. That list is not the Grok list. Each model advertises its own allowed values, so read the model's descriptor before you send a ratio.
What happens if I send a ratio the Grok row does not list?
The docs describe enum parameters as a discrete allowlist of string values, and a request that sets a parameter the selected model does not list is rejected with 400 unsupported_parameter rather than silently dropped. Do not assume Sume forwards a new xAI value the day xAI ships it; the catalog changes first. See also Grok Imagine aspect ratios on Sume.
What should I use for a wide banner today?
Use 20:9 on the Grok row for the widest listed frame. If you need 21:9 or a wider banner exactly, pick a model whose list includes it, or generate at a listed ratio and crop as a post-step. Check wide banner sizes for the crop route.
Sources
Related posts
- Grok Imagine aspect ratio: 21:9 and 5:2 on xAI vs Sume
- Grok Imagine image API: the x-ai/grok-image id on Sume
- Grok Imagine image edit limit: xAI 5 sources, Sume catalog
- AI banner generator: wide banner shapes up to 8:1
- AI image generation API aspect ratios: 4:5, custom sizes, and auto
- Kling 4.0 21:9 ultrawide: check Sume's aspect ratios
More in Models
- Grok Imagine Video 1.5 text-to-video at 1080p: xAI vs Sume
xAI lists native 1080p text-to-video for grok-imagine-video-1.5. Sume's row is image-to-video only at 480p and 720p. How the two differ and what to send.
- HappyHorse 1.0 API: what Runway lists and how to check Sume's models
Runway lists HappyHorse 1.0 at 3-15 seconds, 720p and 1080p. Sume's video docs name no such id, so read /v1/videos/models before you plan around it.
- HappyHorse 1.1 API ids: 480P to 1080P, 3 to 15 seconds
Alibaba lists happyhorse-1.1-t2v, -i2v and -r2v at 480P, 720P or 1080P for 3 to 15 seconds. Sume's catalog docs name HappyHorse 1.1 as not in the v1 catalog.
- Hedra Character 3 aspect ratios vs Sume Avatar Video ratios
Hedra Character 3 lists seven aspect ratios including 9:21 and 21:9. Sume Avatar Video supports five: 1:1, 3:4, 9:16, 4:3 and 16:9, default 9:16.
Written by Sume