What matters
Instagram Story dimensions at a glance
Instagram Stories fill the entire phone screen in a 9:16 vertical format. The top ~250px and bottom ~200px are partially obscured by the username bar and reply input, so critical content should live in the middle.
Working at 1080×1920 matches the native screen canvas. Smaller uploads get scaled up and look blurry; wrong ratios create letterboxing or get center-cropped.
Off-ratio images get awkward bars or auto-zoom cropping. Text placed too high gets hidden behind the username, and text too low gets covered by the reply bar.