It’s because most phones don’t actually rotate the photo, they just add some meta-data that basically says “please rotate X degrees”. That data is often either stripped or ignored when posted online. The best way to deal with this is to open the image in an image editor on your phone and rotate it before submitting.
To add to this, the EXIF data is specifically what is stripped from the image during upload. EXIF data can have a lot of extra details about the image like what camera took it, what settings it used, and even precisely where the photo was taken. Stripping this data is done to protect users from accidentally leaking the GPS location (such as the location of their home).
It’s because most phones don’t actually rotate the photo, they just add some meta-data that basically says “please rotate X degrees”. That data is often either stripped or ignored when posted online. The best way to deal with this is to open the image in an image editor on your phone and rotate it before submitting.
To add to this, the EXIF data is specifically what is stripped from the image during upload. EXIF data can have a lot of extra details about the image like what camera took it, what settings it used, and even precisely where the photo was taken. Stripping this data is done to protect users from accidentally leaking the GPS location (such as the location of their home).