--ar (aspect ratio) controls the frame shape. Midjourney v6 supports anything from 1:5 to 5:1. Choosing the right ratio often improves the image more than changing the prompt.
6 common aspect ratios
| --ar | Typical use | Suggested --s |
|---|---|---|
| 1:1 | E-commerce square, avatars, Instagram | 150–250 |
| 4:5 | E-commerce portrait, IG feed, brand poster | 200–300 |
| 3:4 | Portraits, posters, magazine cover | 150–250 |
| 2:3 | Illustration, traditional art, book cover | 200–400 |
| 16:9 | Horizontal banner, video stills, cinematic | 200–300 |
| 9:16 | Vertical video, phone wallpaper | 200–300 |
How aspect changes composition
The same prompt produces different framings: --ar 1:1 centers, --ar 16:9 reads as a wider landscape, --ar 9:16 favors full-figure or tall vertical compositions. Decide the aspect first, then write the prompt, because composition cues (wide shot / tall composition) need to match.
Workflow tip: Sketch at 1:1 to pick a composition direction, then re-render at the target ratio to avoid stretched results.
Extreme ratios
--ar 21:9 reads as cinematic widescreen. --ar 3:1 suits banners. --ar 1:3 suits long vertical panels. Extreme ratios tend to produce "tiled" artifacts; counter with "single continuous scene" in the prompt.