Facebook carousel ad size

1080 × 1080 square per card, with two to ten cards. Every card has to use the same aspect ratio — mixing them causes the odd ones to be cropped.

The mechanic worth designing around is that Meta reorders cards by performance unless you turn that off. So a carousel built as a sequence — a story told across five cards, or a panorama split into slices — falls apart, because card three may be shown first. If the order matters, disable automatic optimisation in the ad set. If it does not, let it reorder and treat each card as independent. Each card carries its own headline and link, which makes carousels genuinely useful for showing several products rather than as a storytelling device.