Aspect Ratio
The proportional relationship between an image's width and height, written like 16:9 or 1:1. Choosing it is a creative decision, not an afterthought: 1:1 for Instagram feed, 9:16 for Stories, Reels, and TikTok, 16:9 for YouTube and web heroes, 4:5 for portrait feed posts. Set the ratio at generation time — models compose differently for each shape, placing subjects and negative space accordingly — rather than cropping later and losing the composition. Example: the same mountain-sunrise prompt gives a sweeping panorama at 16:9 and an intimate vertical postcard at 9:16.