The vertical stack format solves a specific design problem: how do you show multiple images in a medium that scrolls vertically? The answer is to stack them top-to-bottom in a single file, creating one continuous visual that flows naturally with the user's thumb. This format is essential for Instagram Stories and Reels covers (9:16 vertical), Pinterest Idea Pins (vertical scroll), TikTok video frames (vertical), WhatsApp Status updates (full-screen vertical), and website hero sections designed for mobile. MergeFrame's vertical stacking uses a 3×1, 2×1, or 1×3 layout depending on your photo count — each image is proportionally fitted to equal-width cells that create a seamless vertical column. The key setting for vertical stacks is cell spacing: 0px creates a seamless scroll where images blend into each other, perfect for step-by-step tutorials and narrative sequences. 4–8px spacing creates clean separation that works for product showcases and comparison strips. Export at 1080×1920px for native Story sizing, or 1000×1500px for optimal Pinterest Pin dimensions. Because the vertical stack is a single PNG file, it uploads to any platform that accepts images and displays consistently across devices — no need to worry about carousel sequencing, multi-image upload limits, or platform-specific gallery formatting. MergeFrame processes everything locally, so your vertical stacks are private from creation to publication.