Fit Instagram’s still-image swipe, not every surface
Boxes that belong in the feed
1080×1080 CSS (about 2160 exported) is the grid-native square. 1080×1350 CSS is the taller post that occupies more feed. Mix them and Instagram will letterbox or crop — pick one ratio for the whole ZIP. Keep type off the extreme edges if you will add captions in-app; the composer chrome varies. Cover-fit plus focus pan is how a vertical portrait survives a square slide: drag until the eyes sit in the middle, not on the cut.
Ten vs sixteen, collage vs swipe
The studio allows sixteen slices. Instagram’s feed carousel has long capped at ten. Design ten or fewer if that is the destination, or split into two posts. A collage (one image, many cells) is a different mood — use it when comparison should be simultaneous. A swipe is for sequential reveal: problem, detail, result. Reels and Stories want 9:16; labeling a 4:5 ZIP as a Story pack would be dishonest. Reel covers are a separate still you can approximate with 4:5, then let the app crop.
Upload order is the story
ZIP names are slide-01, slide-02, … Upload in that order. If the OS sorts by “date added,” you can scramble the narrative — sort by name. Instagram will recompress; start from this 2× master, not from screenshots of the filmstrip UI. HEIC from iPhone must be converted before frames appear. Captions, music, and alt text live in Instagram, not here.