You can upload photos up to a size of 15 MB in either JPEG or PNG format.
As of now, the HEIC format is not supported but if you're on an IOS App, the picture will be converted and imported in JPEG.
On a computer:
To find out about the format and size of your file, right-click on the picture and click on " properties/characteristics" .
Type of file = format
Size = weight/size of the picture.