Meta ads run in the feed, stories, Marketplace and the Audience Network, and each placement has its own size. The maker does them all at once: one style, one offer, every shape.
Facebook formats in the maker: ad image 1200×628, post 1080×1080, portrait post 1080×1350, story 1080×1920, cover 1702×630. Tick the ones you need and choose how many picture variants to make for each, from one to four.
Use a square or 4:5 for the feed, 1200×628 for landscape placements and 1080×1920 for stories. Keep copy short: a punchy headline and a button beat long paragraphs. The page cover gets centered text so it isn't cropped on phones.
Pictures are drawn by GPT Image 2.5, Nano Banana, Seedream or FLUX; you pick the model before you start. For shapes the main picture doesn't have, the AI extends its edges, so nothing important gets cropped.