Why photos end up sideways
Cameras do not physically rotate the pixels when you turn the phone — they save the image as the sensor saw it, plus an EXIF orientation tag saying "display me rotated". Software that respects the tag shows the photo upright; software that ignores it shows it sideways. That mismatch is why one photo looks fine in one app and wrong in another.
dotwebp applies the EXIF tag automatically the moment a file loads, then bakes your chosen rotation into the actual pixels. The result displays correctly everywhere — even in software that ignores EXIF entirely.