I always use exiftool to check for metadata in images I upload. I also compress my PNGs with optipng which has a nice ''-strip all'' option that rids the image

I always use exiftool to check for metadata in images I upload. I also compress my PNGs with optipng which has a nice ''-strip all'' option that rids the image of metadata, which you can then doublecheck with exiftool. For file types you're not familiar with, you can simply open the file in a text editor and check for the presence details you don't want in there. This only works for checking, though.