Use Capture more when it works
Take a normal screenshot and look for Capture more, Scroll or a downward-arrow control. Select the region and save. This native result is usually preferable because the operating system can capture content outside the visible viewport.
Use separate screenshots as a fallback
If the button does not appear or the result repeats a toolbar, take a sequence of ordinary screenshots with visible overlap. Keep the same orientation and avoid scrolling while a message, ad or animation is changing.
Join and correct the result
Add the images to TallMerge, put them in order, and run smart overlap trim. The preview makes duplicated rows obvious. Use manual top and bottom crop controls for seams where the app's header stays fixed or dynamic content changed.
Export at a practical size
PNG is best for text-heavy screens. If the output is extremely tall, a 1080 pixel width keeps memory and file size under control while remaining readable on most phones.